Dropbox (DBX) 10-Q 10 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 06, 2019
Document Information [Line Items]
Entity Registrant Name	Dropbox, Inc.
Entity Central Index Key	0001467623
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Emerging Growth Company	false
Entity Small Business	false
Amendment Flag	false
Class A common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		227,146,748
Class B common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		242,146,748
Class C common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		0

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents		$ 359.2	$ 519.3
Short-term investments		556	570
Trade and other receivables, net		34.1	28.6
Prepaid expenses and other current assets		58.3	92.3
Total current assets		1,007.6	1,210.2
Property and equipment, net		340.9	310.6
Operating lease right-of-use asset		430.4
Intangible assets, net		57.4	14.7
Goodwill		230.4	96.5
Other assets		61.9	62.1
Total assets		2,128.6	1,694.1
Current liabilities:
Accounts payable		27.4	33.3
Accrued and other current liabilities		148.8	164.5
Accrued compensation and benefits		36.4	80.9
Operating lease liability		74.1
Finance lease obligation		70.7
Finance lease obligation			73.8
Deferred revenue		508.4	485
Total current liabilities		865.8	837.5
Operating lease liability, non-current		441.5
Finance lease obligation, non-current	[1]	106.7
Finance lease obligation, non-current	[1]		89.9
Other non-current liabilities		9.7	89.9
Total liabilities		1,423.7	1,017.3
Commitments and contingencies (Note 10)
Stockholders’ equity:
Additional paid-in capital		2,377.8	2,337.5
Accumulated deficit		(1,674.7)	(1,659.5)
Accumulated other comprehensive income (loss)		1.8	(1.2)
Total stockholders’ equity		704.9	676.8
Total liabilities and stockholders’ equity		$ 2,128.6	$ 1,694.1
[1]	As of December 31, 2018 the Company had non-current deferred rent of $81.0 million. As of March 31, 2019, deferred rent is now included in the determination of the Company's operating lease right-of-use asset due to the adoption of ASC 842.

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenue		$ 385.6	$ 316.3
Cost of revenue	[1],[2]	98.4	120.6
Gross profit		287.2	195.7
Operating expenses
Research and development	[1],[2]	150	378.5
Sales and marketing	[1],[2]	101.5	157
General and administrative	[1],[2]	57	126.1
Total operating expenses	[1],[2]	308.5	661.6
Loss from operations		(21.3)	(465.9)
Interest income (expense), net		3.7	(1.2)
Other income, net		4.2	3.4
Loss before income taxes		(13.4)	(463.7)
Benefit from (provision for) income taxes		5.7	(1.8)
Net loss		$ (7.7)	$ (465.5)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)		$ (0.02)	$ (2.13)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)		410.5	218.8
[1]	During the three months ended March 31, 2018, the Company recognized the cumulative unrecognized stock-based compensation of $418.7 million related to two-tier restricted stock units upon the effectiveness of the registration statement for the Company's IPO. See Note 1, "Description of the Business and Summary of Significant Accounting Policies" for further information.
[2]	Includes stock-based compensation as follows (in millions): for the three months ended June 30, 2018 and 2017: Cost of revenues of 3.0 million and 37.8 million . Research and development of 30.5 million and 282.9 million. Sales and marketing 7.1 million and 72.4 million. General and administrative of 15.0 million and 93.4 million, respectively.

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) $ in Millions	Dec. 31, 2018USD ($)
Statement of Financial Position [Abstract]
Non-current deferred rent	$ 81

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cost of revenue
Allocated share-based compensation expense	$ 3	$ 37.8
Research and development
Allocated share-based compensation expense	30.5	282.9
Sales and marketing
Allocated share-based compensation expense	7.1	72.4
General and administrative
Allocated share-based compensation expense	$ 15	$ 93.4

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (7.7)	$ (465.5)
Other comprehensive income (loss), net of tax:
Change in foreign currency translation adjustments	1.1	1.5
Change in net unrealized gains (losses) on short-term investments	1.9	(0.1)
Total other comprehensive income (loss), net of tax	3	1.4
Comprehensive loss	$ (4.7)	$ (464.1)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Convertible preferred stock	Class A and Class B common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive income (loss)
Shares outstanding, beginning of the period (in shares) at Dec. 31, 2017		147.6	196.8
Shareholders equity, beginning balance at Dec. 31, 2017	$ 102.9	$ 615.3	$ 0	$ 533.1	$ (1,049.7)	$ 4.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Release of restricted stock units (in shares)			30.6
Release of restricted stock units	0
Shares repurchased for tax withholdings on release of restricted stock (in shares)			(11.8)
Shares repurchased for tax withholdings on release of restricted stock	(247.3)			(162.1)	(85.2)
Conversion of preferred stock to common stock in connection with initial public offering (in shares)		(147.6)	147.6
Conversion of preferred stock to common stock in connection with initial public offering	0	$ (615.3)		615.3
Issuance of common stock in connection with initial public offering and private placement, net of underwriters' discounts and commissions and issuance costs (in shares)			31.6
Issuance of common stock in connection with initial public offering and private placement, net of underwriters' discounts and commissions and issuance costs	631.3			631.3
Exercise of stock options and awards (in shares)			0.2
Exercise of stock options and awards	0.8			0.8
Stock-based compensation	486.5			486.5
Other comprehensive income	1.4					1.4
Net loss	(465.5)				(465.5)
Shares outstanding, end of the period (in shares) at Mar. 31, 2018		0	395
Shareholders equity, ending balance at Mar. 31, 2018	510.1	$ 0	$ 0	2,104.9	(1,600.4)	5.6
Shares outstanding, beginning of the period (in shares) at Dec. 31, 2018		0	409.6
Shareholders equity, beginning balance at Dec. 31, 2018	676.8	$ 0	$ 0	2,337.5	(1,659.5)	(1.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Release of restricted stock units (in shares)			2.6
Release of restricted stock units	$ 0
Shares repurchased for tax withholdings on release of restricted stock (in shares)	(1)		(1)
Shares repurchased for tax withholdings on release of restricted stock	$ (25.5)			(17)	(8.5)
Exercise of stock options and awards (in shares)	0.2		0.2
Exercise of stock options and awards	$ 0.9			0.9
Assumed stock options in connection with acquisition	0.8			0.8
Stock-based compensation	55.6			55.6
Other comprehensive income	3					3
Net loss	(7.7)
Net loss | Accounting Standards Update 2016-02	(7.7)
Shares outstanding, end of the period (in shares) at Mar. 31, 2019		0	411.4
Shareholders equity, ending balance at Mar. 31, 2019	$ 704.9	$ 0	$ 0	$ 2,377.8	$ (1,674.7)	$ 1.8

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Cash flow from operating activities
Net loss	$ (7.7)	$ (465.5)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	45.8	35.9
Stock-based compensation	55.6	486.5
Amortization of deferred commissions	3.9	2.4
Other	(4.4)	(0.6)
Changes in operating assets and liabilities:
Trade and other receivables, net	(5.1)	3.6
Prepaid expenses and other current assets	(14.2)	(1.5)
Other assets	11.2	(5.7)
Accounts payable	(5.2)	(2.8)
Accrued and other current liabilities	10	8.8
Accrued compensation and benefits	(45.9)	(26.2)
Deferred revenue	18.6	26.7
Other non-current liabilities	(13.2)	0.2
Tenant improvement allowance reimbursement	13.8	0
Net cash provided by operating activities	63.2	61.8
Cash flow from investing activities
Capital expenditures	(29.7)	(9.9)
Cash paid for business combinations, net of cash acquired	(172.1)	0
Purchases of short-term investments	(153)	(180.8)
Proceeds from sales of short-term investments	110.2	0
Proceeds from maturities of short-term investments	66.6	0
Other	4.7	(2.4)
Net cash used in investing activities	(173.3)	(193.1)
Cash flow from financing activities
Proceeds from initial public offering and private placement, net of underwriters' discounts and commissions	0	638.2	$ 746.6
Payments of deferred offering costs	0	(0.9)
Shares repurchased for tax withholdings on release of restricted stock	(25.5)	(241.2)
Proceeds from issuance of common stock, net of repurchases	0.9	0.8
Principal payments on finance lease obligations	(26.2)
Principal payments on finance lease obligations		(29.8)
Other	(0.2)	(2.1)
Net cash (used in) provided by financing activities	(51)	365
Effect of exchange rate changes on cash and cash equivalents	1	1.6
Change in cash and cash equivalents	(160.1)	235.3
Cash and cash equivalents—beginning of period	519.3	430	430
Cash and cash equivalents—end of period	359.2	665.3	$ 519.3
Supplemental cash flow data:
Property and equipment acquired under finance leases	$ 39.9
Property and equipment acquired under finance leases		$ 25.5

Description of the Business and

Description of the Business and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the Business and Summary of Significant Accounting Policies	Description of the Business and Summary of Significant Accounting Policies Business Dropbox, Inc. (the “Company” or “Dropbox”) is a global collaboration platform. Dropbox was incorporated in May 2007 as Evenflow, Inc., a Delaware corporation, and changed its name to Dropbox, Inc. in October 2009. The Company is headquartered in San Francisco, California. Basis of presentation and consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the United States of America generally accepted accounting principles (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission ("SEC") regarding interim financial reporting. The accompanying unaudited condensed consolidated financial statements include the accounts of Dropbox and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The condensed consolidated balance sheet as of December 31, 2018 included herein was derived from the audited financial statements as of that date. The unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the balance sheets, statements of operations, statements of comprehensive loss, statements of stockholders' equity and the statements of cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full fiscal year ended December 31, 2019 or any future period. The unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the related notes thereto as of and for the year ended December 31, 2018 , included in the Company's Annual Report on Form 10-K on file with the SEC ("Annual Report"). Initial public offering and private placement On March 27, 2018, the Company closed its initial public offering ("IPO"), in which the Company issued and sold 26,822,409 shares of Class A common stock at $21.00 per share. The Company received aggregate proceeds of $538.2 million , net of underwriters' discounts and commissions, before deducting offering costs of $6.9 million , net of reimbursements. Immediately prior to the closing of the Company’s IPO, 147,310,563 shares of convertible preferred stock outstanding converted into an equivalent number of shares of Class B common stock. Further, pursuant to transfer agreements with certain of the Company’s stockholders, 258,620 shares of the Company’s convertible preferred stock and 2,609,951 shares of the Company’s Class B common stock automatically converted into an equivalent number of shares of Class A common stock. Immediately subsequent to the closing of the Company's IPO, Salesforce Ventures LLC purchased 4,761,905 shares of Class A common stock from the Company at $21.00 per share. The Company received aggregate proceeds of $100.0 million and did not pay any underwriting discounts or commissions with respect to the shares that were sold in the private placement. On March 28, 2018, the underwriters exercised their option to purchase an additional 5,400,000 shares of the Company's Class A common stock at $21.00 per share. This transaction closed on April 3, 2018, resulting in additional proceeds of $108.4 million , net of underwriters' discounts and commissions. The Company’s net proceeds from the IPO, the concurrent private placement, and underwriters' option totaled $ 746.6 million , before deducting offering costs of $ 6.9 million , net of reimbursements. Upon the effectiveness of the registration statement for the Company's IPO, which was March 22, 2018, the liquidity event-related performance vesting condition, referred to as the Performance Vesting Condition, associated with the Company's two-tier restricted stock units ("RSUs") was satisfied. As a result, the Company recognized the cumulative unrecognized stock-based compensation related to its two-tier RSUs using the accelerated attribution method of $418.7 million attributable to service prior to such effective date. During the first quarter of 2018, the Company's Board of Directors approved the acceleration of the Performance Vesting Condition for which the service condition was satisfied, to occur upon the effectiveness of the registration statement for the Company's IPO, rather than six months following an IPO. As a result, the Company released 26.8 million shares of common stock underlying the two-tier RSUs for which the Performance Vesting Condition was satisfied, and recorded $13.9 million in employer related payroll tax expenses associated with these same awards. Stock split On March 7, 2018, the Company effected a 1-for-1.5 reverse stock split of its capital stock. All of the share and per share information referenced throughout the condensed consolidated financial statements and notes to the condensed consolidated financial statements have been retroactively adjusted to reflect this reverse stock split. Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the Company’s condensed consolidated financial statements and accompanying notes. These estimates are based on information available as of the date of the condensed consolidated financial statements. Management evaluates these estimates and assumptions on a regular basis. Actual results may differ materially from these estimates. The Company’s most significant estimates and judgments involve the estimation of the fair value of market-based awards and the valuation of acquired intangible assets and goodwill from business combinations. Financial information about segments and geographic areas The Company manages its operations and allocates resources as a single operating segment. Further, the Company manages, monitors, and reports its financials as a single reporting segment. The Company’s chief operating decision-maker is its Chief Executive Officer, who reviews financial information presented on a consolidated basis for purposes of making operating decisions, assessing financial performance, and allocating resources. See Note 16, "Geographic Areas" for information regarding the Company’s long-lived assets and revenue by geography. Foreign currency transactions The assets and liabilities of the Company’s foreign subsidiaries are translated from their respective functional currencies into U.S. dollars at the exchange rates in effect at the balance sheet date. Revenue and expense amounts are translated at the average exchange rate for the period. Foreign currency translation gains and losses are recorded in other comprehensive income (loss). Gains and losses realized from foreign currency transactions (those transactions denominated in currencies other than the foreign subsidiaries’ functional currency) are included in other income (expense), net. Monetary assets and liabilities are remeasured using foreign currency exchange rates at the end of the period, and non-monetary assets are remeasured based on historical exchange rates. The Company recorded immaterial net foreign currency transaction gains during the three months ended March 31, 2019 and 2018 , respectively. Revenue recognition The Company derives its revenue from subscription fees from customers for access to its platform. The Company’s policy is to exclude sales and other indirect taxes when measuring the transaction price of its subscription agreements. The Company accounts for revenue contracts with customers through the following steps: • Identification of the contract, or contracts, with a customer • Identification of the performance obligations in the contract • Determination of the transaction price • Allocation of the transaction price to the performance obligations in the contract • Recognition of revenue when, or as, the Company satisfies a performance obligation The Company’s subscription agreements generally have monthly or annual contractual terms and a small percentage have multi-year contractual terms. Revenue is recognized ratably over the related contractual term beginning on the date that the platform is made available to a customer. Access to the platform represents a series of distinct services as the Company continually provides access to, and fulfills its obligation to the end customer over the subscription term. The series of distinct services represents a single performance obligation that is satisfied over time. The Company recognizes revenue ratably because the customer receives and consumes the benefits of the platform throughout the contract period. The Company’s contracts are generally non-cancelable. The Company bills in advance for monthly contracts and typically bills annually in advance for contracts with terms of one year or longer . The Company also recognizes an immaterial amount of contract assets, or unbilled receivables, primarily relating to consideration for services completed but not billed at the reporting date. Unbilled receivables are classified as receivables when the Company has the right to invoice the customer. The Company records contract liabilities when cash payments are received or due in advance of performance to deferred revenue. Deferred revenue primarily relates to the advance consideration received from the customer. The price of subscriptions is generally fixed at contract inception and therefore, the Company’s contracts do not contain a significant amount of variable consideration. As a result, the amount of revenue recognized in the periods presented from performance obligations satisfied (or partially satisfied) in previous periods was not material. The Company recognized $222.6 million and $188.2 million of revenue during the three months ended March 31, 2019 , and 2018 , respectively, that was included in the deferred revenue balances at the beginning of their respective periods. As of March 31, 2019 , future estimated revenue related to performance obligations that were unsatisfied or partially unsatisfied was $549.8 million . The substantial majority of the unsatisfied performance obligations will be satisfied over the next twelve months. Stock-based compensation The Company has granted RSUs to its employees and members of the Board of Directors under the 2008 Equity Incentive Plan (“2008 Plan”), the 2017 Equity Incentive Plan (“2017 Plan”), and the 2018 Equity Incentive Plan ("2018 Plan"). The Company had two types of RSUs outstanding as of March 31, 2019 : • One-tier RSUs, which have a service-based vesting condition over a four -year period. These awards typically have a cliff vesting period of one year and continue to vest quarterly thereafter. The Company began granting one-tier RSUs under its 2008 Plan in August 2015 and it continues to grant one-tier RSUs under its 2018 Plan. The Company recognizes compensation expense associated with one-tier RSUs ratably on a straight-line basis over the requisite service period and accounts for forfeitures in the period in which they occur. • Two-tier RSUs, which have both a service-based vesting condition and a Performance Vesting Condition. The service-based vesting period for these awards is typically four years with a cliff vesting period of one year and continue to vest monthly thereafter. Upon satisfaction of the Performance Vesting Condition, these awards vest quarterly. The Performance Vesting Condition was satisfied on the effectiveness of the registration statement related to the Company's IPO. Prior to August 2015, the Company granted two-tier RSUs under the 2008 Plan. The last grant date for two-tier RSUs was in May 2015. The Company recognizes compensation expense associated with two-tier RSUs using the accelerated attribution method over the requisite service period. The Performance Vesting Condition for the two-tier RSUs was satisfied upon the effectiveness of the registration statement related to the Company's IPO, which was March 22, 2018. On that date, the Company recognized the cumulative unrecognized expense of the two-tier RSUs, using the accelerated attribution method, which is included in the Company's results for the three months ended March 31, 2018 . See "—Initial public offering and private placement” for further discussion. Since August 2015, the Company has granted one-tier RSUs as the only stock-based payment awards to its employees, with the exception of awards granted to its co-founders, and has not granted any stock options to employees since then. The fair values of the common stock underlying the RSUs granted in periods prior to the date of the Company's IPO were determined by the Board of Directors, with input from management and contemporaneous third-party valuations, which were performed at least quarterly. For valuations after the Company's IPO, the Board of Directors determines the fair value of each share of underlying common stock based on the closing price of the Company's Class A common stock as reported on the Nasdaq Global Select Market on the date of the grant. In connection with the acquisition of JN Projects, Inc. (d/b/a HelloSign) ("HelloSign"), the Company assumed unvested stock options that had been granted under the HelloSign's 2011 Equity Incentive Plan. The fair value of options assumed were based upon the Black-Scholes option-pricing model, see Note 12, "Stockholders' Equity" for further information. In December 2017, the Board of Directors approved a grant to the Company’s co-founders of restricted stock awards (“RSAs”) with respect to 14.7 million shares of Class A Common Stock in the aggregate (collectively, the “Co-Founder Grants”), of which 10.3 million RSAs were granted to Mr. Houston, the Company’s co-founder and Chief Executive Officer, and 4.4 million RSAs were granted to Mr. Ferdowsi, the Company’s co-founder and Director. These Co-Founder Grants have service-based, market-based, and performance-based vesting conditions. The Company estimated the grant date fair value of the Co-Founder Grants using a model based on multiple stock price paths developed through the use of a Monte Carlo simulation that incorporates into the valuation the possibility that the Stock Price Targets may not be satisfied. See Note 12, "Stockholders' Equity" for further information. Cash and cash equivalents Cash consists primarily of cash on deposit with banks and includes amounts in transit from payment processors for credit and debit card transactions, which typically settle within five business days. Cash equivalents include highly liquid investments purchased with an original maturity date of 90 days or less from the date of purchase. Short-term investments The Company’s short-term investments are primarily comprised of corporate notes and obligations, U.S. treasury securities, certificates of deposits, U.S. agency obligations, and commercial paper. The Company determines the appropriate classification of its short-term investments at the time of purchase and reevaluates such designation at each balance sheet date. The Company has classified and accounted for its short-term investments as available-for-sale securities as the Company may sell these securities at any time for use in its current operations or for other purposes, even prior to maturity. As a result, the Company classifies its short-term investments, including securities with stated maturities beyond twelve months, within current assets in the condensed consolidated balance sheets. The Company's short-term investments are classified as available-for-sale securities and are recorded at fair value each reporting period. Unrealized gains and losses on these short-term investments are reported as a separate component of accumulated other comprehensive income (loss) in the condensed consolidated balance sheets until realized. Interest income is reported within interest income (expense), net in the condensed consolidated statements of operations. The Company periodically evaluates its short-term investments to assess whether those with unrealized loss positions are other-than-temporarily impaired. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time the investment has been in a loss position, the extent to which the fair value is less than the Company’s cost basis, and the financial condition and near-term prospects of the investee. Realized gains and losses are determined based on the specific identification method and are reported in other income (expense), net in the condensed consolidated statements of operations. If the Company determines that the decline in an investment’s fair value is other-than-temporary, the difference is recognized as an impairment loss in the condensed consolidated statements of operations. Concentrations of credit risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, accounts receivable, and short-term investments. The Company places its cash and cash equivalents and short-term investments with well-established financial institutions. Trade accounts receivables are typically unsecured and are derived from revenue earned from customers located around the world. Two customers accounted for 13% and 41% of total trade and other receivables, net as of March 31, 2019 . Two customers accounted for 14% and 23% of total trade and other receivables, net as of December 31, 2018 . No customer accounted for more than 10% of the Company’s revenue in the periods presented. Non-trade receivables The Company records non-trade receivables to reflect amounts due for activities outside of its subscription agreements, such as receivables resulting from tenant improvement allowances prior to the adoption of ASC 842. Non-trade receivables totaled $10.3 million and $46.2 million , as of March 31, 2019 and December 31, 2018 , respectively, and are classified within prepaid expenses and other current assets and other assets in the accompanying condensed consolidated balance sheets. See "—Lease obligations” for further discussion. Deferred commissions, net Deferred commissions, net is stated as gross deferred commissions less accumulated amortization. Sales commissions earned by the Company’s sales force and third-party resellers, as well as related payroll taxes, are considered to be incremental and recoverable costs of obtaining a contract with a customer. These amounts have been capitalized as deferred commissions within prepaid and other current assets and other assets on the condensed consolidated balance sheets. The Company deferred incremental costs of obtaining a contract of $ 7.3 million and $9.8 million during the three months ended March 31, 2019 and 2018 , respectively. Deferred commissions, net included in prepaid and other current assets were $15.9 million and $14.5 million as of March 31, 2019 and December 31, 2018 , respectively. Deferred commissions, net included in other assets were $40.3 million and $38.3 million as of March 31, 2019 and December 31, 2018 , respectively. Deferred commissions are typically amortized over a period of benefit of five years. The period of benefit was estimated by considering factors such as historical customer attrition rates, the useful life of the Company’s technology, and the impact of competition in its industry. Amortized costs were $ 3.9 million and $2.4 million for the three months ended March 31, 2019 and 2018 , respectively. Amortized costs are included in sales and marketing expense in the accompanying condensed consolidated statements of operations. There was no impairment loss in relation to the deferred costs for any period presented. Property and equipment, net Equipment is stated at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful life of the related asset, which is generally three to seven years. Leasehold improvements are amortized on a straight-line basis over the shorter of their estimated useful lives or the term of the related lease. The following table presents the estimated useful lives of property and equipment: Property and equipment Useful life Buildings 20 to 30 years Datacenter and other computer equipment 3 to 5 years Office equipment and other 3 to 7 years Leasehold improvements Lesser of estimated useful life or remaining lease term Lease obligations The Company leases office space, datacenters, and equipment under non-cancelable finance and operating leases with various expiration dates through 2033. The Company determines if an arrangement contains a lease at inception. Operating lease right-of-use assets and lease liabilities are recognized at the present value of the future lease payments at commencement date. The interest rate implicit in the Company’s operating leases is not readily determinable, and therefore an incremental borrowing rate is estimated to determine the present value of future payments. The estimated incremental borrowing rate factors in a hypothetical interest rate on a collateralized basis with similar terms, payments, and economic environments. Operating lease right-of-use assets also include any prepaid lease payments and lease incentives. Certain of the operating lease agreements contain rent concession, rent escalation, and option to renew provisions. Rent concession and rent escalation provisions are considered in determining the straight-line single lease cost to be recorded over the lease term. Single lease cost is recognized on a straight-line basis over the lease term commencing on the date the Company has the right to use the leased property. The lease terms may include options to extend or terminate the lease. The Company generally uses the base, non-cancelable, lease term when recognizing the lease assets and liabilities, unless it is reasonably certain that the option will be exercised. In addition, certain of the Company’s operating lease agreements contain tenant improvement allowances from its landlords. These allowances are accounted for as lease incentives and decrease the Company's right-of-use asset and reduce single lease cost over the lease term. The Company leases certain equipment from various third parties, through equipment financing leases. These leases either include a bargain purchase option, a full transfer of ownership at the completion of the lease term, or the terms of the leases are at least 75 percent of the useful lives of the assets and are therefore classified as finance leases. These leases are capitalized in property and equipment and the related amortization of assets under finance leases is included in depreciation and amortization expense in the Company’s condensed consolidated statements of operations. Initial asset values and finance lease obligations are based on the present value of future minimum lease payments. The Company’s finance lease agreements may contain lease and non-lease components. The non-lease components include payments for support on infrastructure equipment obtained via finance leases, which when not significant in relation to the overall agreement, are combined with the lease components and accounted for together as a single lease component. Business combinations The Company uses best estimates and assumptions to assign a fair value to the tangible and intangible assets acquired and liabilities assumed in business combinations as of the acquisition date. These estimates are inherently uncertain and subject to refinement. During the measurement period, which may be up to one year from the acquisition date, adjustments to the fair value of these tangible and intangible assets acquired and liabilities assumed may be recorded, with the corresponding offset to goodwill. Upon the conclusion of the measurement period or final determination of the fair value of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to the Company’s consolidated statements of operations. Long-lived assets, including goodwill and other acquired intangible assets, net The Company evaluates the recoverability of its property and equipment and finite-lived intangible assets for possible impairment whenever events or circumstances indicate that the carrying amount of such assets may not be recoverable. The evaluation is performed at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities. Recoverability of these assets is measured by a comparison of the carrying amounts to the future undiscounted cash flows the assets are expected to generate. If such review determines that the carrying amount of specific property and equipment or intangible assets is not recoverable, the carrying amount of such assets is reduced to its fair value. The Company reviews goodwill for impairment at least annually in the fourth quarter, or more frequently if events or changes in circumstances would more likely than not reduce the fair value of its single reporting unit below its carrying value. The Company has not recorded impairment charges on property and equipment, goodwill, or intangible assets for the periods presented in these condensed consolidated financial statements. Acquired property and equipment and finite-lived intangible assets are amortized over their useful lives. The Company evaluates the estimated remaining useful life of these assets when events or changes in circumstances warrant a revision to the remaining period of amortization. If the Company revises the estimated useful life assumption for any asset, the remaining unamortized balance is amortized or depreciated over the revised estimated useful life on a prospective basis. Income taxes Deferred income tax balances reflect the effects of temporary differences between the financial reporting and tax bases of the Company’s assets and liabilities using enacted tax rates expected to apply when taxes are actually paid or recovered. In addition, deferred tax assets are recorded for net operating loss and credit carryforwards. A valuation allowance is provided against deferred tax assets unless it is more likely than not that they will be realized based on all available positive and negative evidence. Such evidence includes, but is not limited to, recent cumulative earnings or losses, expectations of future taxable income by taxing jurisdiction, and the carry-forward periods available for the utilization of deferred tax assets. The Company uses a two-step approach to recognizing and measuring uncertain income tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates it is more likely than not that the position will be sustained on audit. The second step is to measure the tax benefit as the largest amount which is more than 50% likely of being realized upon ultimate settlement. The Company recognizes interest and penalties related to unrecognized tax benefits as income tax expense. Although the Company believes that it has adequately reserved for its uncertain tax positions, it can provide no assurance that the final tax outcome of these matters will not be materially different. The Company evaluates its uncertain tax positions on a regular basis and evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, such as the 2017 Tax Cuts and Jobs Act ("2017 Tax Reform Act"), correspondence with tax authorities during the course of an audit, and effective settlement of audit issues. To the extent that the final tax outcome of these matters is different than the amounts recorded, such differences will affect the provision for income taxes in the period in which such determination is made and could have a material impact on the Company’s financial condition and results of operations. Fair value measurement The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. The Company defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value measurements for assets and liabilities, the Company considers the principal or most advantageous market in which it would transact and the market-based risk measurements or assumptions that market participants would use in pricing the asset or liability, such as risks inherent in valuation techniques, transfer restrictions, and credit risk. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1 —Quoted prices in active markets for identical assets or liabilities. Level 2 —Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 —Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability. Recently issued accounting pronouncements not yet adopted In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost. It also eliminates the concept of other-than-temporary impairment and requires credit losses related to available-for-sale debt securities to be recorded through an allowance for credit losses rather than as a reduction in the amortized cost basis of the securities. These changes will result in more timely recognition of credit losses. The guidance is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact of adopting ASU No. 2016-13. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820), which amends disclosure requirements for fair value measurements by requiring new disclosures, modifying existing requirements, and eliminating others. The amendments are the result of a broader disclosure project, which aims to improve the effectiveness of disclosures. ASU No. 2018-13 is effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years. Early adoption is permitted. The Company does not expect the adoption to have a significant impact on its disclosures and is currently evaluating the timing of adopting ASU No. 2018-13. In August 2018, the FASB issued ASU No. 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40), Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. Under existing U.S. GAAP, there is diversity in practice in accounting for the costs of implementing cloud computing arrangements that are service contracts. The amendments in ASU No. 2018-15 amend the definition of a hosting arrangement and requires a customer in a hosting arrangement that is a service contract to capitalize certain costs as if the arrangement were an internal-use software project. The guidance is effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact and timing of adopting ASU No. 2018-15. Recently adopted accounting pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) . Most prominent among the changes in the standard is the recognition of right-of-use assets (“ROU assets”) and lease liabilities by lessees for certain leases classified as operating leases under current GAAP. The Company has made the policy election to not recognize a lease liability or right-of-use asset for short-term operating leases. The Company adopted the standard as of

Cash, Cash Equivalents and Shor

Cash, Cash Equivalents and Short-Term Investments	3 Months Ended
	Mar. 31, 2019
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents and Short-Term Investments	Cash, Cash Equivalents and Short-Term Investments The amortized cost, unrealized gains and losses and estimated fair value of the Company's cash, cash equivalents and short-term investments as of March 31, 2019 and December 31, 2018 consisted of the following: As of March 31, 2019 Amortized Cost Unrealized Gain Unrealized Loss Estimated Fair Value Cash $ 109.8 $ — $ — $ 109.8 Cash equivalents: Money market funds 226.9 — — 226.9 Commercial paper 19.5 — — 19.5 Corporate notes and obligations 3.0 — — 3.0 Total cash and cash equivalents $ 359.2 $ — $ — $ 359.2 Investments Corporate notes and obligations 244.7 0.6 — 245.3 U.S. Treasury securities 193.0 — (0.1 ) 192.9 Certificates of deposit 52.2 — — 52.2 U.S. agency obligations 38.5 — — 38.5 Commercial Paper 27.1 — — 27.1 Total short-term investments 555.5 0.6 (0.1 ) 556.0 Total $ 914.7 $ 0.6 $ (0.1 ) $ 915.2 As of December 31, 2018 Amortized cost Unrealized gain Unrealized loss Estimated fair value Cash $ 103.0 $ — $ — $ 103.0 Cash equivalents Money market funds 355.5 — — 355.5 U.S. Treasury securities 33.4 — — $ 33.4 Commercial paper 27.4 — — 27.4 Total cash and cash equivalents $ 519.3 $ — $ — $ 519.3 Short-term investments Corporate notes and obligations 269.6 0.1 (0.5 ) 269.2 U.S. Treasury securities 176.0 — (0.1 ) 175.9 Certificates of deposit 70.6 — — 70.6 U.S. agency obligations 37.1 — — 37.1 Commercial paper 17.2 — — 17.2 Total short-term investments 570.5 0.1 (0.6 ) 570.0 Total $ 1,089.8 $ 0.1 $ (0.6 ) $ 1,089.3 Included in cash and cash equivalents is cash in transit from payment processors for credit and debit card transactions of $15.8 million and $11.9 million as of March 31, 2019 and December 31, 2018 , respectively. All short-term investments were designated as available-for-sale securities as of March 31, 2019 and December 31, 2018 . The following table presents the contractual maturities of the Company’s short-term investments as of March 31, 2019 : As of March 31, 2019 Amortized cost Estimated fair value Due within one year $ 337.9 $ 338.1 Due between one to three years 217.6 217.9 Total $ 555.5 $ 556.0 The Company had 65 short-term investments in unrealized loss positions as of March 31, 2019 . There were no material gross unrealized losses from available-for-sale securities and no material realized gains or losses from available-for-sale securities that were reclassified out of accumulated other comprehensive income for the three months ended March 31, 2019 and 2018 . For investments in available-for-sale debt securities that have unrealized losses, the Company evaluates whether (i) it has the intention to sell any of these investments and (ii) whether it is not more likely than not that it will be required to sell any of these investments before recovery of the entire amortized cost basis. Based on this evaluation, the Company determined that there were no other-than-temporary impairments associated with short-term investments as of March 31, 2019 . The Company recorded $6.2 million and $1.4 million in interest income from its cash, cash equivalents and short-term investments for the three months ended March 31, 2019 and 2018 , respectively.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company measures its financial instruments at fair value each reporting period using a fair value hierarchy that prioritizes the use of observable inputs and minimizes the use of unobservable inputs when measuring fair value. A financial instrument’s classification within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The following table presents information about the Company’s financial instruments that are measured at fair value on a recurring basis using the input categories discussed in Note 1: As of March 31, 2019 Level 1 Level 2 Level 3 Total Cash equivalents Money market funds $ 226.9 $ — $ — $ 226.9 Commercial paper — 19.5 — 19.5 Corporate notes and obligations — 3.0 — 3.0 Total cash equivalents $ 226.9 $ 22.5 $ — $ 249.4 Short-term investments Corporate notes and obligations — 245.3 — 245.3 U.S. Treasury securities — 192.9 — 192.9 Certificates of deposit — 52.2 — 52.2 U.S. agency obligations — 38.5 — 38.5 Commercial paper — 27.1 — 27.1 Total short-term investments — 556.0 — 556.0 Total cash equivalents and short-term investments $ 226.9 $ 578.5 $ — $ 805.4 As of December 31, 2018 Level 1 Level 2 Level 3 Total Cash equivalents Money market funds $ 355.5 $ — $ — $ 355.5 U.S. Treasury securities — 33.4 — 33.4 Commercial paper — 27.4 — 27.4 Total cash equivalents $ 355.5 $ 60.8 $ — $ 416.3 Short-term investments Corporate notes and obligations — 269.2 — 269.2 U.S. treasury securities — 175.9 — 175.9 Certificates of deposit — 70.6 — 70.6 U.S agency obligations — 37.1 — 37.1 Commercial paper — 17.2 — 17.2 Total short-term investments — $ 570.0 — 570.0 Total cash equivalents and short-term investments $ 355.5 $ 630.8 $ — $ 986.3 The Company had no transfers between levels of the fair value hierarchy. The carrying amounts of certain financial instruments, including cash held in banks, accounts receivable and accounts payable approximate fair value due to their short-term maturities and are excluded from the fair value table above.

Property and Equipment, Net

Property and Equipment, Net	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net consisted of the following: As of March 31, 2019 December 31, 2018 Datacenter and other computer equipment $ 682.8 $ 667.4 Furniture and fixtures 24.8 23.8 Leasehold improvements 153.8 150.5 Construction in process 60.6 32.8 Total property and equipment 922.0 874.5 Accumulated depreciation and amortization (581.1 ) (563.9 ) Property and equipment, net $ 340.9 $ 310.6 The Company leases certain infrastructure from various third parties, through equipment financing leases. Infrastructure assets as of March 31, 2019 and December 31, 2018 , respectively included a total of $ 360.2 million and $362.8 million acquired under financing lease agreements. These leases are capitalized in property and equipment, and the related amortization of assets under financing leases is included in depreciation and amortization expense. The accumulated depreciation of the infrastructure under financing leases totaled $ 196.2 million and $211.7 million as of March 31, 2019 and December 31, 2018 , respectively. Construction in process includes costs primarily related to construction of leasehold improvements for office buildings and datacenters. Depreciation expense related to property and equipment was $ 43.1 million and $ 34.1 million for the three months ended March 31, 2019 and 2018 , respectively.

Business Combinations

Business Combinations	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Business Combinations	Business Combinations On February 8, 2019, the Company acquired all outstanding stock of JN Projects, Inc. (d/b/a HelloSign) ("HelloSign"), which provides an e-signature and document workflow platform. The acquisition of HelloSign expands the Company's content collaboration capabilities to include additional business-critical workflows. The results of HelloSign operations have been included in the Company’s consolidated results of operations since the date of acquisition. The purchase consideration transferred consisted of the following: Purchase consideration Cash paid to common and preferred stockholders and vested option holders $ 175.2 Transaction costs paid by Dropbox on behalf of HelloSign 2.4 Fair value of assumed HelloSign options attributable to pre-combination services (1) 0.8 Purchase price adjustments (0.8 ) Total purchase consideration $ 177.6 (1) The fair value of option assumed were based upon the Black-Scholes option-pricing model. In addition to the total purchase consideration above, the Company has compensation agreements with key HelloSign personnel consisting of $48.5 million in future cash payments subject to on-going employee service. The related expense will be recognized within research and development expenses over the required service period of three years, while the related payments will begin in the first quarter of 2020 if the requisite service is provided. The purchase consideration was preliminarily allocated to the tangible and intangible assets and liabilities acquired as of the acquisition date, with the excess recorded to goodwill as shown below. The fair value of assets and liabilities acquired may change as additional information is received during the measurement period. The measurement period will end no later than one-year from the acquisition date. Assets acquired: Cash and cash equivalents $ 5.5 Short-term investments 7.8 Acquisition-related intangible assets 44.6 Accounts receivable, prepaid and other assets 5.0 Total assets acquired $ 62.9 Liabilities assumed: Accounts payable, accrued and other liabilities $ 6.3 Deferred revenue 4.8 Deferred tax liability 6.9 Total liabilities assumed 18.0 Net assets acquired, excluding goodwill 44.9 Total purchase consideration 177.6 Estimated goodwill (2) $ 132.7 (2) The goodwill recognized was primarily attributable to the opportunity to expand the user base of the Company's platform. The goodwill is not deductible for U.S. federal income tax purposes. The fair value of the separately identifiable finite-lived intangible assets acquired and estimated weighted average useful lives are as follows: Estimated fair values Estimated weighted average useful lives (In years) Customer relationships $ 20.5 4.9 Developed technology 19.6 5.0 Trade name 4.5 5.0 Total acquisition-related intangible assets $ 44.6 The fair values of the acquisition-related intangibles were determined using the following methodologies: the multi-period excess earnings method, replacement cost method, and the relief from royalty method, for customer relationships, developed technology, and the trade name, respectively. The valuation model inputs required the application of significant judgment by management. The acquired intangible assets have a total weighted average amortization period of 4.9 years. One-time acquisition-related diligence costs of $1.0 million were expensed within general and administrative expenses as incurred during the three months ended March 31, 2019 .

Intangible Assets

Intangible Assets	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	Intangible Assets Intangible assets consisted of the following: As of March 31, As of December 31, Weighted- (In years) 2019 2018 Developed technology $ 25.0 $ 47.0 4.9 Customer relationships 20.5 — 4.8 Software 20.0 19.2 2.2 Patents 13.0 13.0 7.9 Assembled workforce in asset acquisitions 12.6 12.6 1.6 Licenses 4.6 4.6 2.2 Trademarks and trade names 5.2 0.7 4.9 Other 3.3 3.3 6.0 Total intangibles 104.2 100.4 Accumulated amortization (46.8 ) (85.7 ) Intangible assets, net $ 57.4 $ 14.7 During the three months ended March 31, 2019 the Company retired $41.7 million in fully amortized developed technology assets. Amortization expense was $2.8 million and $1.8 million for the three months ended March 31, 2019 and 2018 , respectively. Expected future amortization expense for intangible assets as of March 31, 2019 , is as follows: Remaining nine months of Fiscal 2019 $ 10.8 2020 13.6 2021 11.3 2022 8.0 2023 7.7 Thereafter 6.0 Total $ 57.4

Goodwill

Goodwill	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill Goodwill represents the excess of the purchase price in a business combination over the fair value of net tangible and intangible assets acquired. The changes in the carrying amounts of goodwill were as follows: Balance at December 31, 2018 $ 96.5 HelloSign acquisition 132.7 Effect of foreign currency translation 1.2 Balance at March 31, 2019 $ 230.4 The goodwill acquired from HelloSign is carried in U.S. dollars, while goodwill from previous acquisitions is denominated in other foreign currencies. Goodwill amounts are not amortized, but tested for impairment on an annual basis. There was no impairment of goodwill as of March 31, 2019 and December 31, 2018 .

Revolving Credit Facility

Revolving Credit Facility	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Revolving Credit Facility	Revolving Credit Facility In April 2017, the Company entered into an amended and restated credit and guaranty agreement which provided for a $600.0 million revolving loan facility (the “revolving credit facility”). In conjunction with the revolving credit facility, the Company paid upfront issuance fees of $2.6 million , which are being amortized over the five -year term of the agreement. In February 2018, the Company amended its revolving credit facility to, among other things, permit the Company to make certain investments, enter into an unsecured standby letter of credit facility and increase its standby letter of credit sublimit to $187.5 million . The Company increased its borrowing capacity under the revolving credit facility from $600.0 million to $725.0 million . The Company may from time to time request increases in its borrowing capacity under the revolving credit facility of up to $275.0 million , provided no event of default has occurred or is continuing or would result from such increase. In conjunction with the amendment, the Company paid upfront issuance fees of $0.4 million , which are being amortized over the remaining term of the agreement. Pursuant to the terms of the revolving credit facility, the Company may issue letters of credit under the revolving credit facility, which reduce the total amount available for borrowing. Pursuant to the terms of the revolving credit facility, the Company is required to pay an annual commitment fee that accrues at a rate of 0.20% per annum on the unused portion of the borrowing commitments under the revolving credit facility. In addition, the Company is required to pay a fee in connection with letters of credit issued under the revolving credit facility, which accrues at a rate of 1.5% per annum on the amount of such letters of credit outstanding. There is an additional fronting fee of 0.125% per annum multiplied by the average aggregate daily maximum amount available under all letters of credit. Borrowings under the revolving credit facility bear interest, at the Company’s option, at an annual rate based on LIBOR plus a spread of 1.50% or at an alternative base rate plus a spread of 0.50% . The revolving credit facility contains customary conditions to borrowing, events of default and covenants, including covenants that restrict the Company’s ability to incur indebtedness, grant liens, make distributions to holders of the Company or its subsidiaries’ equity interests, make investments, or engage in transactions with its affiliates. In addition, the revolving credit facility contains financial covenants, including a consolidated leverage ratio covenant and a minimum liquidity balance of $100.0 million , which includes any available borrowing capacity. The Company was in compliance with the covenants of the revolving credit facility as of March 31, 2019 and December 31, 2018 , respectively. The Company had an aggregate of $68.9 million of letters of credit outstanding under the revolving credit facility as of March 31, 2019 , and the Company’s total available borrowing capacity under the revolving credit facility was $656.1 million as of March 31, 2019 . The Company’s letters of credit expire between April of 2019 and April of 2022 .

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases	Leases The Company has operating leases for corporate offices and datacenters, and finance leases for infrastructure equipment. The Company’s leases have remaining lease terms of 1 year to 15 years, some of which include options to extend the leases for up to 5 years. The Company also has subleases of former corporate offices. Subleases have remaining lease terms of 3 to 4 years. Sublease income, which is recorded as a reduction of rental expense, was $1.9 million and $3.5 million for the three months ended March 31, 2019 and 2018 , respectively. The components of single lease cost were as follows: Three months ended March 31, 2019 March 31, 2018 Operating lease cost (1) $ 22.1 $ 21.9 Finance lease cost: Amortization of assets under finance lease 21.7 21.7 Interest 2.2 1.9 Total finance lease cost $ 23.9 $ 23.6 (1) Is presented gross of sublease income and includes short-term leases, which are immaterial Other information related to leases was as follows: Three months ended March 31, 2019 Supplemental Cash Flow Information: Cash paid for amounts included in the measurement of lease liabilities: Payments for operating leases included in cash from operating activities $ 23.0 Payments for finance leases included in cash from operating activities $ 2.2 Payments for finance leases included in cash from financing activities $ 26.2 Assets obtained in exchange for lease obligations: Operating leases $ 14.5 Finance leases $ 39.9 Weighted Average Remaining Lease Term (in years) Operating leases 9.7 Finance leases 2.8 Weighted Average Discount Rate Operating leases 4.4 % Finance leases 5.1 % Future minimum lease payments under non-cancellable leases as of March 31, 2019 were as follows: Year ending December 31, Operating leases (1) Finance leases 2019 (excluding the three months ended March 31, 2019) $ 64.8 $ 64.2 2020 84.6 56.2 2021 77.6 41.1 2022 70.3 27.4 2023 53.4 2.2 Thereafter 357.0 — Total future minimum lease payments 707.7 191.1 Less imputed interest (163.6 ) (13.7 ) Less tenant improvement receivables (28.5 ) — Total liability $ 515.6 $ 177.4 (1) Consists of future non-cancelable minimum rental payments under operating leases for the Company’s corporate offices and datacenters where the Company has possession, excluding rent payments from the Company’s sub-tenants and variable operating expenses. As of March 31, 2019, the Company is entitled to non-cancelable rent payments from its sub-tenants of $40.6 million, which will be collected over the next 4 years . In 2017, the Company entered into a lease agreement for office space in San Francisco, California, to serve as its new corporate headquarters. The Company took initial possession of the first phase of its new corporate headquarters in June 2018, and began to recognize single lease cost. In that same period, the Company recorded a lease incentive obligation related to tenant improvement reimbursements associated with the first phase. The lease incentive obligation is recorded net against the Company's operating right-of-use asset and was $ 42.6 million as of March 31, 2019. The Company expects to start making recurring rental payments under the lease in the third quarter of 2019. The Company's total expected minimum obligations for all three phases of the lease are $ 843.1 million, which exclude expected tenant improvement reimbursements from the landlord of approximately $75.0 million and variable operating expenses. The Company’s obligations under the lease are supported by a $34.2 million letter of credit, which reduced the borrowing capacity under the revolving credit facility. In the three months ended March 31, 2019, the Company collected tenant improvement reimbursements from the landlord totaling $ 13.8 million. As of March 31, 2019 , the Company had commitments of $408.3 million for operating leases that have not yet commenced, and therefore are not included in the right-of-use asset or operating lease liability. These operating leases will commence between 2019 and 2021 with lease terms of 4 years to 15 years.
Leases	Leases The Company has operating leases for corporate offices and datacenters, and finance leases for infrastructure equipment. The Company’s leases have remaining lease terms of 1 year to 15 years, some of which include options to extend the leases for up to 5 years. The Company also has subleases of former corporate offices. Subleases have remaining lease terms of 3 to 4 years. Sublease income, which is recorded as a reduction of rental expense, was $1.9 million and $3.5 million for the three months ended March 31, 2019 and 2018 , respectively. The components of single lease cost were as follows: Three months ended March 31, 2019 March 31, 2018 Operating lease cost (1) $ 22.1 $ 21.9 Finance lease cost: Amortization of assets under finance lease 21.7 21.7 Interest 2.2 1.9 Total finance lease cost $ 23.9 $ 23.6 (1) Is presented gross of sublease income and includes short-term leases, which are immaterial Other information related to leases was as follows: Three months ended March 31, 2019 Supplemental Cash Flow Information: Cash paid for amounts included in the measurement of lease liabilities: Payments for operating leases included in cash from operating activities $ 23.0 Payments for finance leases included in cash from operating activities $ 2.2 Payments for finance leases included in cash from financing activities $ 26.2 Assets obtained in exchange for lease obligations: Operating leases $ 14.5 Finance leases $ 39.9 Weighted Average Remaining Lease Term (in years) Operating leases 9.7 Finance leases 2.8 Weighted Average Discount Rate Operating leases 4.4 % Finance leases 5.1 % Future minimum lease payments under non-cancellable leases as of March 31, 2019 were as follows: Year ending December 31, Operating leases (1) Finance leases 2019 (excluding the three months ended March 31, 2019) $ 64.8 $ 64.2 2020 84.6 56.2 2021 77.6 41.1 2022 70.3 27.4 2023 53.4 2.2 Thereafter 357.0 — Total future minimum lease payments 707.7 191.1 Less imputed interest (163.6 ) (13.7 ) Less tenant improvement receivables (28.5 ) — Total liability $ 515.6 $ 177.4 (1) Consists of future non-cancelable minimum rental payments under operating leases for the Company’s corporate offices and datacenters where the Company has possession, excluding rent payments from the Company’s sub-tenants and variable operating expenses. As of March 31, 2019, the Company is entitled to non-cancelable rent payments from its sub-tenants of $40.6 million, which will be collected over the next 4 years . In 2017, the Company entered into a lease agreement for office space in San Francisco, California, to serve as its new corporate headquarters. The Company took initial possession of the first phase of its new corporate headquarters in June 2018, and began to recognize single lease cost. In that same period, the Company recorded a lease incentive obligation related to tenant improvement reimbursements associated with the first phase. The lease incentive obligation is recorded net against the Company's operating right-of-use asset and was $ 42.6 million as of March 31, 2019. The Company expects to start making recurring rental payments under the lease in the third quarter of 2019. The Company's total expected minimum obligations for all three phases of the lease are $ 843.1 million, which exclude expected tenant improvement reimbursements from the landlord of approximately $75.0 million and variable operating expenses. The Company’s obligations under the lease are supported by a $34.2 million letter of credit, which reduced the borrowing capacity under the revolving credit facility. In the three months ended March 31, 2019, the Company collected tenant improvement reimbursements from the landlord totaling $ 13.8 million. As of March 31, 2019 , the Company had commitments of $408.3 million for operating leases that have not yet commenced, and therefore are not included in the right-of-use asset or operating lease liability. These operating leases will commence between 2019 and 2021 with lease terms of 4 years to 15 years.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal matters From time to time, the Company is a party to a variety of claims, lawsuits, and proceedings which arise in the ordinary course of business, including claims of alleged infringement of intellectual property rights. The Company records a liability when it believes that it is probable that a loss will be incurred and the amount of loss or range of loss can be reasonably estimated. In its opinion, resolution of pending matters is not likely to have a material adverse impact on its consolidated results of operations, cash flows, or its financial position. Given the unpredictable nature of legal proceedings, the Company bases its estimate on the information available at the time of the assessment. As additional information becomes available, the Company reassesses the potential liability and may revise the estimate. Indemnification The Company’s arrangements generally include certain provisions for indemnifying customers against liabilities if its products or services infringe a third party’s intellectual property rights. It is not possible to determine the maximum potential amount under these indemnification obligations due to the limited history of prior indemnification claims. Other commitments Other commitments include payments to third-party vendors for services related to the Company’s infrastructure, infrastructure warranty contracts, asset retirement obligations for office modifications, and a note payable related to financing of infrastructure. There have been no material changes in the Company's other commitments, as disclosed in the Annual Report.

Accrued and Other Current Liabi

Accrued and Other Current Liabilities	3 Months Ended
	Mar. 31, 2019
Payables and Accruals [Abstract]
Accrued and Other Current Liabilities	Accrued and Other Current Liabilities Accrued and other current liabilities consisted of the following: As of March 31, 2019 December 31, 2018 Non-income taxes payable $ 83.9 $ 75.7 Accrued legal and other external fees 34.2 28.1 Deferred rent — 41.0 Income taxes payable (0.1 ) 0.3 Other accrued and current liabilities 30.8 19.4 Total accrued and other current liabilities $ 148.8 $ 164.5 The decrease in deferred rent from December 31, 2018 is due to the Company's adoption of ASC 842 on January 1, 2019 using the modified retrospective approach. As of March 31, 2019 , deferred rent reduces the Company's operating right-of-use asset. See Note 9 "Leases" for additional discussion.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2019
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Common stock The Company’s amended and restated certificate of incorporation authorizes the issuance of Class A common stock, Class B common stock, and Class C common stock. Holders of Class A common stock, Class B common stock, and Class C common stock are entitled to dividends on a pro rata basis, when, as, and if declared by the Company’s Board of Directors, subject to the rights of the holders of the Company’s preferred stock. Holders of Class A common stock are entitled to one vote per share, holders of Class B common stock are entitled to 10 votes per share, and holders of Class C common stock are entitled to zero votes per share. During the three months ended March 31, 2019 , holders of 11.8 million shares of Class B common stock voluntarily converted into an equivalent number of shares of Class A common stock. As of March 31, 2019 , the Company had authorized 2,400.0 million shares of Class A common stock, 475.0 million shares of Class B common stock, and 800.0 million shares of Class C common stock, each at par value of $0.00001 . As of March 31, 2019 , 224.1 million shares of Class A common stock, 187.3 million shares of Class B common stock, and no shares of Class C common stock were issued and outstanding. As of December 31, 2018 , 211.0 million shares of Class A common stock, 198.6 million shares of Class B common stock, and no shares of Class C common stock were issued and outstanding. Class A shares issued and outstanding as of March 31, 2019 and December 31, 2018 exclude 14.7 million unvested restricted stock awards granted to the Company’s co-founders. See "Co-Founder Grants" section below for further details. Convertible preferred stock Immediately prior to the closing of the Company’s IPO, all of the 147.3 million shares of convertible preferred stock converted into an equivalent number of shares of Class B common stock. Further, pursuant to transfer agreements with certain of the Company’s stockholders, 0.3 million shares of the Company’s convertible preferred stock automatically converted into an equivalent number of shares of Class A common stock. Preferred stock The Company's Board of Directors will have the authority, without further action by the Company's stockholders, to issue up to 240.0 million shares of undesignated preferred stock with rights and preferences, including voting rights, designated from time to time by the Board of Directors. Equity incentive plans Under the 2018 Plan, the Company may grant stock-based awards to purchase or directly issue shares of common stock to employees, directors, and consultants. Options are granted at a price per share equal to the fair market value of the Company's common stock at the date of grant. Options granted are exercisable over a maximum term of 10 years from the date of grant and generally vest over a period of four years. RSUs and RSAs are also granted under the 2018 Plan. The 2018 Plan will terminate 10 years after the later of (i) its adoption or (ii) the most recent stockholder-approved increase in the number of shares reserved under the 2018 Plan, unless terminated earlier by the Company's Board of Directors. The 2018 Plan was adopted on March 22, 2018. In connection with the acquisition of HelloSign, the Company assumed unvested stock options that had been granted under the HelloSign's 2011 Equity Incentive Plan. As of March 31, 2019 , there were 25.4 million stock-based awards issued and outstanding and 79.2 million shares available for issuance under the 2008 Equity Incentive Plan, HelloSign's Equity Incentive Plan, the 2017 Equity Incentive Plan, and the 2018 Plan (collectively, the "Plans"). Stock option and restricted stock activity for the Plans was as follows for the three months ended March 31, 2019 : Options outstanding Restricted stock outstanding Number of shares available for issuance under the Plans Number of shares outstanding under the Plans Weighted- average exercise price per share Weighted- average remaining contractual term (In years) Aggregate intrinsic value Number of shares outstanding under the Plans Weighted- average grant date fair value per share Balance at December 31, 2018 57.1 1.3 $ 14.68 5.0 $ 9.1 25.0 $ 18.68 Additional shares authorized 21.2 — — — — Stock options assumed 0.9 0.9 6.02 — — Options exercised and RSUs released — (0.2 ) 5.15 (2.6 ) 17.42 Options and RSUs canceled 1.5 — — (1.5 ) 17.19 Shares repurchased for tax withholdings on release of restricted stock 1.0 — — — 17.42 Restricted stock and options granted (2.5 ) 0.2 22.63 2.3 23.79 Balance at March 31, 2019 79.2 2.2 $ 12.45 5.1 $ 21.7 23.2 $ 19.44 Vested at March 31, 2019 1.1 $ 15.71 5.1 $ 7.7 — $ — Unvested at March 31, 2019 1.1 $ 9.22 $ 14.0 23.2 $ 19.44 The following table summarizes information about the pre-tax intrinsic value of options exercised during the three months ended March 31, 2019 and 2018 : Three months ended March 31, 2019 2018 Intrinsic value of options exercised $ 3.1 $ 1.7 As of March 31, 2019 , unamortized stock-based compensation related to unvested stock options, restricted stock awards (excluding the Co-Founder Grants), and RSUs was $447.8 million . The weighted-average period over which such compensation expense will be recognized if the requisite service is provided is approximately 3.0 years as of March 31, 2019 . The total fair value of released RSUs, as of their respective vesting dates, during the three months ended March 31, 2019 and 2018 were $67.9 million and $643.3 million , respectively. Assumed stock options In connection with the acquisition of HelloSign the Company assumed 0.9 million unvested stock options which were valued using the Black-Scholes option-pricing model. The fair value of stock options assumed were estimated using the following assumptions: Expected volatility 51.6 % Expected term (in years) 3.4 - 7.0 Risk-free interest rate 2.42% - 2.51% Dividend yield — % Expected volatility. The expected volatility is based on the Company's historical volatility. Management believes this is the best estimate of the expected volatility over the expected life of its stock options. Expected term. The Company determines the expected term based on the average period the stock options are expected to remain outstanding, generally calculated as the midpoint of the stock options’ remaining vesting term and contractual expiration period, as the Company does not have sufficient historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior. Risk-free interest rate . The risk-free interest rate is based on the U.S. Treasury security in effect at the time the options were assumed for maturities corresponding with the expected term of the option. Expected dividend yield . The Company has not paid and does not expect to pay dividends. Consequently, the Company uses an expected dividend yield of zero . The estimated weighted-average grant date fair value for stock options assumed was $21.60 per share and total fair value of $ 19.4 million , of which, $18.6 million will be recognized as post-combination stock-based compensation expense. Co-Founder Grants In December 2017, the Board of Directors approved a grant to the Company’s co-founders of non-Plan RSAs with respect to 14.7 million shares of Class A Common Stock in the aggregate (collectively, the “Co-Founder Grants”), of which 10.3 million RSAs were granted to Mr. Houston, the Company’s co-founder and Chief Executive Officer, and 4.4 million RSAs were granted to Mr. Ferdowsi, the Company’s co-founder and Director. These Co-Founder Grants have service-based, market-based, and performance-based vesting conditions. The Co-Founder Grants are excluded from Class A common stock issued and outstanding until the satisfaction of these vesting conditions. The Co-Founder Grants also provide the holders with certain stockholder rights, such as the right to vote the shares with the other holders of Class A common stock and a right to cumulative declared dividends. However, the Co-Founder Grants are not considered a participating security for purposes of calculating net loss per share attributable to common stockholders in Note 13, "Net Loss Per Share", as the right to the cumulative declared dividends is forfeitable if the service condition is not met. The Co-Founder Grants are eligible to vest over the ten -year period following the date the Company’s shares of Class A common stock commenced trading on the Nasdaq Global Select Market in connection with the Company’s IPO. The Co-Founder Grants comprise nine tranches that are eligible to vest based on the achievement of stock price goals, each of which are referred to as a Stock Price Target, measured over a consecutive thirty-day trading period during the Performance Period. The Performance Period began on January 1, 2019. During the first four years of the Performance Period, no more than 20% of the shares subject to each Co-Founder Grant would be eligible to vest in any calendar year. After the first four years, all shares are eligible to vest based on the achievement of the Stock Price Targets. The Company calculated the grant date fair value of the Co-Founder Grants based on multiple stock price paths developed through the use of a Monte Carlo simulation. A Monte Carlo simulation also calculates a derived service period for each of the nine vesting tranches, which is the measure of the expected time to achieve each Stock Price Target. A Monte Carlo simulation requires the use of various assumptions, including the underlying stock price, volatility, and the risk-free interest rate as of the valuation date, corresponding to the length of time remaining in the performance period, and expected dividend yield. The weighted-average grant date fair value of each Co-Founder Grant was estimated to be $10.60 per share. The weighted-average derived service period of each Co-Founder Grant was estimated to be 5.2 years, and ranged from 2.9 - 6.9 years. The Company will recognize aggregate stock-based compensation expense of $156.2 million over the derived service period of each tranche using the accelerated attribution method as long as the co-founders satisfy their service-based vesting conditions. If the Stock Price Targets are met sooner than the derived service period, the Company will adjust its stock-based compensation to reflect the cumulative expense associated with the vested awards. The Company will recognize expense if the requisite service is provided, regardless of whether the market conditions are achieved. The Performance Vesting Condition for the Co-Founder Grants was satisfied on the date the Company’s shares of Class A common stock commenced trading on the Nasdaq Global Select Market in connection with the Company’s IPO, which was March 23, 2018. The Company recognized $8.6 million and $10.6 million in stock-based compensation related to the Co-Founder Grants during the three months ended March 31, 2019 and 2018 , respectively. As of March 31, 2019 , unamortized stock-based compensation expense related to the Co-Founder Grants was $119.3 million . Award modifications During the year ended December 31, 2017, the Company's Board of Directors voted to approve a modification of vesting schedules for certain unvested one-tier and two-tier RSUs to align the vesting schedules for all RSUs to vest once per quarter. The modification was effective February 15, 2018, which resulted in accelerated vesting of impacted RSUs that had met their service requirement as of that date. As a result, the Company recognized an incremental $10.0 million in stock-based compensation during the first quarter of 2018 related to these modified one-tier and two-tier RSUs.

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share The Company computes net loss per share using the two-class method required for multiple classes of common stock and participating securities. The rights, including the liquidation and dividend rights, of the Class A common stock and Class B common stock are substantially identical, other than voting rights. Accordingly, the Class A common stock and Class B common stock share equally in the Company’s net losses. Before the IPO, the Company’s outstanding securities also included convertible preferred stock. The holders of convertible preferred stock did not have a contractual obligation to share in the Company’s losses, and as a result, net losses were not allocated to these securities. The following table sets forth the calculation of basic and diluted net loss per share attributable to common stockholders during the periods presented. The shares issued in the IPO and the shares of Class A and Class B common stock issued upon conversion of the outstanding shares of convertible preferred stock in the IPO are included in the table below weighted for the period outstanding in the three months ended March 31, 2018 . Additionally, the voluntary conversions of Class B common stock into Class A common stock are included in the table below weighted for the period outstanding in the three months ended March 31, 2019 : Three months ended March 31, 2019 2018 Class A Class B Class A Class B Numerator: Net loss attributable to common stockholders $ (4.0 ) $ (3.7 ) $ (30.8 ) $ (434.7 ) Denominator: Weighted-average number of common shares outstanding used in computing basic and diluted net loss per common share 215.1 195.4 14.5 204.3 Net loss per common share, basic and diluted $ (0.02 ) $ (0.02 ) $ (2.13 ) $ (2.13 ) Since the Company was in a loss position for all periods presented, basic net loss per share attributable to common stockholders is the same as diluted net loss per share for all periods as the inclusion of all potential common shares outstanding would have been anti-dilutive. The weighted-average impact of potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive was as follows: Three months ended 2019 2018 Restricted stock units 24.6 56.3 Options to purchase shares of common stock 1.8 4.9 Co-Founder Grants 14.7 14.7 Total 41.1 75.9

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company computed the year-to-date income tax provision by applying the estimated annual effective tax rate to the year-to-date pre-tax loss and adjusted for discrete tax items in the period. The Company's income tax was a benefit of $5.7 million for the three months ended March 31, 2019 , and an expense of $1.8 million for the three months ended March 31, 2018 . Income tax benefit for the three months ended March 31, 2019 was primarily attributable to the tax benefit from the acquisition of HelloSign. During the three months ended March 31, 2019 , the Company recorded a deferred tax liability of $6.9 million to reflect the tax effect of the assets and liabilities recorded in the acquisition of HelloSign. As a result of the acquisition of HelloSign, the Company recorded a one-time benefit of $6.9 million to recognize previously unrecognized deferred tax assets, which are now more-likely-than-not to be realized as a result of the net deferred tax liability recorded in the transaction. For further discussion of the HelloSign acquisition, see Note 5 "Business Combinations". For the periods presented, the difference between the U.S. statutory rate and the Company's effective tax rate is primarily due to the full valuation allowance on its U.S. and Irish deferred tax assets. The effective tax rate is also impacted by earnings realized in foreign jurisdictions with statutory tax rates lower than the federal statutory tax rate. The Company periodically evaluates the realizability of its net deferred tax assets based on all available evidence, both positive and negative. The realization of net deferred tax assets is dependent on the Company's ability to generate sufficient future taxable income during periods prior to the expiration of tax attributes to fully utilize these assets. As of March 31, 2019 , the Company continues to maintain a full valuation allowance on its deferred tax assets in the U.S. and Ireland. However, the Company has partially benefited from its deferred tax assets due to the recognition of forecasted future income which is more likely than not to be earned in one of its foreign jurisdictions. The Company is subject to income tax audits in the U.S. and foreign jurisdictions. The Company records liabilities related to uncertain tax positions and believes that it has provided adequate reserves for income tax uncertainties in all open tax years. Unrecognized tax benefits increased by approximately $3.6 million for the three months ended March 31, 2019 , of which $0.6 million , if recognized, would affect the Company's effective tax rate.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2019
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Dropbox Charitable Foundation During the year ended December 31, 2016, two of the Company’s controlling shareholders formed the Dropbox Charitable Foundation, a Delaware non-stock corporation (the “Foundation”). The primary purpose of the Foundation is to engage in charitable and educational activities within the meaning of Section 501(c)(3) of the Code. The Foundation is governed by a Board of Directors, a majority of which are independent. Both shareholders made contributions to the Foundation during the year ended December 31, 2016, comprised entirely of shares of Dropbox common stock. The Company has not consolidated the Foundation in the accompanying condensed consolidated financial statements, as the Company does not have control of the entity. There were no contributions to the Foundation during the three months ended March 31, 2019 and 2018 , respectively.

Geographic Areas

Geographic Areas	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Geographic Areas	Geographic Areas Long-lived assets The following table sets forth long-lived assets by geographic area: As of March 31, 2019 December 31, 2018 United States $ 324.9 $ 293.6 International (1) 16.0 17.0 Total property and equipment, net $ 340.9 $ 310.6 (1) No single country other than the United States had a property and equipment balance greater than 10% of total property and equipment, net, as of March 31, 2019 and December 31, 2018 . Revenue Revenue by geography is generally based on the address of the customer as defined in the Company’s subscription agreement. The following table sets forth revenue by geographic area for the three months ended March 31, 2019 and 2018 . Three months ended March 31, 2019 2018 United States $ 197.1 $ 161.6 International (1) 188.5 154.7 Total revenue $ 385.6 $ 316.3 (1) No single country outside of the United States accounted for more than 10% of total revenue during the three months ended March 31, 2019 and 2018 , respectively.

Description of the Business a_2

Description of the Business and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the United States of America generally accepted accounting principles (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission ("SEC") regarding interim financial reporting. The accompanying unaudited condensed consolidated financial statements include the accounts of Dropbox and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Basis of consolidation	The condensed consolidated balance sheet as of December 31, 2018 included herein was derived from the audited financial statements as of that date. The unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the balance sheets, statements of operations, statements of comprehensive loss, statements of stockholders' equity and the statements of cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full fiscal year ended December 31, 2019 or any future period. The unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the related notes thereto as of and for the year ended December 31, 2018 , included in the Company's
Use of estimates	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the Company’s condensed consolidated financial statements and accompanying notes. These estimates are based on information available as of the date of the condensed consolidated financial statements. Management evaluates these estimates and assumptions on a regular basis. Actual results may differ materially from these estimates. The Company’s most significant estimates and judgments involve the estimation of the fair value of market-based awards and the valuation of acquired intangible assets and goodwill from business combinations.
Financial information about segments and geographic areas	The Company manages its operations and allocates resources as a single operating segment. Further, the Company manages, monitors, and reports its financials as a single reporting segment. The Company’s chief operating decision-maker is its Chief Executive Officer, who reviews financial information presented on a consolidated basis for purposes of making operating decisions, assessing financial performance, and allocating resources.
Foreign currency transactions	The assets and liabilities of the Company’s foreign subsidiaries are translated from their respective functional currencies into U.S. dollars at the exchange rates in effect at the balance sheet date. Revenue and expense amounts are translated at the average exchange rate for the period. Foreign currency translation gains and losses are recorded in other comprehensive income (loss). Gains and losses realized from foreign currency transactions (those transactions denominated in currencies other than the foreign subsidiaries’ functional currency) are included in other income (expense), net. Monetary assets and liabilities are remeasured using foreign currency exchange rates at the end of the period, and non-monetary assets are remeasured based on historical exchange rates.
Revenue recognition and deferred commissions, net	The Company derives its revenue from subscription fees from customers for access to its platform. The Company’s policy is to exclude sales and other indirect taxes when measuring the transaction price of its subscription agreements. The Company accounts for revenue contracts with customers through the following steps: • Identification of the contract, or contracts, with a customer • Identification of the performance obligations in the contract • Determination of the transaction price • Allocation of the transaction price to the performance obligations in the contract • Recognition of revenue when, or as, the Company satisfies a performance obligation The Company’s subscription agreements generally have monthly or annual contractual terms and a small percentage have multi-year contractual terms. Revenue is recognized ratably over the related contractual term beginning on the date that the platform is made available to a customer. Access to the platform represents a series of distinct services as the Company continually provides access to, and fulfills its obligation to the end customer over the subscription term. The series of distinct services represents a single performance obligation that is satisfied over time. The Company recognizes revenue ratably because the customer receives and consumes the benefits of the platform throughout the contract period. The Company’s contracts are generally non-cancelable. The Company bills in advance for monthly contracts and typically bills annually in advance for contracts with terms of one year or longer . The Company also recognizes an immaterial amount of contract assets, or unbilled receivables, primarily relating to consideration for services completed but not billed at the reporting date. Unbilled receivables are classified as receivables when the Company has the right to invoice the customer. The Company records contract liabilities when cash payments are received or due in advance of performance to deferred revenue. Deferred revenue primarily relates to the advance consideration received from the customer. The price of subscriptions is generally fixed at contract inception and therefore, the Company’s contracts do not contain a significant amount of variable consideration. Deferred commissions, net is stated as gross deferred commissions less accumulated amortization. Sales commissions earned by the Company’s sales force and third-party resellers, as well as related payroll taxes, are considered to be incremental and recoverable costs of obtaining a contract with a customer. These amounts have been capitalized as deferred commissions within prepaid and other current assets and other assets on the condensed consolidated balance sheets.
Stock-based compensation	The Company has granted RSUs to its employees and members of the Board of Directors under the 2008 Equity Incentive Plan (“2008 Plan”), the 2017 Equity Incentive Plan (“2017 Plan”), and the 2018 Equity Incentive Plan ("2018 Plan"). The Company had two types of RSUs outstanding as of March 31, 2019 : • One-tier RSUs, which have a service-based vesting condition over a four -year period. These awards typically have a cliff vesting period of one year and continue to vest quarterly thereafter. The Company began granting one-tier RSUs under its 2008 Plan in August 2015 and it continues to grant one-tier RSUs under its 2018 Plan. The Company recognizes compensation expense associated with one-tier RSUs ratably on a straight-line basis over the requisite service period and accounts for forfeitures in the period in which they occur. • Two-tier RSUs, which have both a service-based vesting condition and a Performance Vesting Condition. The service-based vesting period for these awards is typically four years with a cliff vesting period of one year and continue to vest monthly thereafter. Upon satisfaction of the Performance Vesting Condition, these awards vest quarterly. The Performance Vesting Condition was satisfied on the effectiveness of the registration statement related to the Company's IPO. Prior to August 2015, the Company granted two-tier RSUs under the 2008 Plan. The last grant date for two-tier RSUs was in May 2015. The Company recognizes compensation expense associated with two-tier RSUs using the accelerated attribution method over the requisite service period. The Performance Vesting Condition for the two-tier RSUs was satisfied upon the effectiveness of the registration statement related to the Company's IPO, which was March 22, 2018. On that date, the Company recognized the cumulative unrecognized expense of the two-tier RSUs, using the accelerated attribution method, which is included in the Company's results for the three months ended March 31, 2018 . See "—Initial public offering and private placement” for further discussion. Since August 2015, the Company has granted one-tier RSUs as the only stock-based payment awards to its employees, with the exception of awards granted to its co-founders, and has not granted any stock options to employees since then. The fair values of the common stock underlying the RSUs granted in periods prior to the date of the Company's IPO were determined by the Board of Directors, with input from management and contemporaneous third-party valuations, which were performed at least quarterly. For valuations after the Company's IPO, the Board of Directors determines the fair value of each share of underlying common stock based on the closing price of the Company's Class A common stock as reported on the Nasdaq Global Select Market on the date of the grant. In connection with the acquisition of JN Projects, Inc. (d/b/a HelloSign) ("HelloSign"), the Company assumed unvested stock options that had been granted under the HelloSign's 2011 Equity Incentive Plan. The fair value of options assumed were based upon the Black-Scholes option-pricing model, see Note 12, "Stockholders' Equity" for further information. In December 2017, the Board of Directors approved a grant to the Company’s co-founders of restricted stock awards (“RSAs”) with respect to 14.7 million shares of Class A Common Stock in the aggregate (collectively, the “Co-Founder Grants”), of which 10.3 million RSAs were granted to Mr. Houston, the Company’s co-founder and Chief Executive Officer, and 4.4 million RSAs were granted to Mr. Ferdowsi, the Company’s co-founder and Director. These Co-Founder Grants have service-based, market-based, and performance-based vesting conditions. The Company estimated the grant date fair value of the Co-Founder Grants using a model based on multiple stock price paths developed through the use of a Monte Carlo simulation that incorporates into the valuation the possibility that the Stock Price Targets may not be satisfied. See Note 12, "Stockholders' Equity" for further information.
Cash and cash equivalents	Cash consists primarily of cash on deposit with banks and includes amounts in transit from payment processors for credit and debit card transactions, which typically settle within five business days. Cash equivalents include highly liquid investments purchased with an original maturity date of 90 days or less from the date of purchase.
Short-term investments	The Company’s short-term investments are primarily comprised of corporate notes and obligations, U.S. treasury securities, certificates of deposits, U.S. agency obligations, and commercial paper. The Company determines the appropriate classification of its short-term investments at the time of purchase and reevaluates such designation at each balance sheet date. The Company has classified and accounted for its short-term investments as available-for-sale securities as the Company may sell these securities at any time for use in its current operations or for other purposes, even prior to maturity. As a result, the Company classifies its short-term investments, including securities with stated maturities beyond twelve months, within current assets in the condensed consolidated balance sheets. The Company's short-term investments are classified as available-for-sale securities and are recorded at fair value each reporting period. Unrealized gains and losses on these short-term investments are reported as a separate component of accumulated other comprehensive income (loss) in the condensed consolidated balance sheets until realized. Interest income is reported within interest income (expense), net in the condensed consolidated statements of operations. The Company periodically evaluates its short-term investments to assess whether those with unrealized loss positions are other-than-temporarily impaired. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time the investment has been in a loss position, the extent to which the fair value is less than the Company’s cost basis, and the financial condition and near-term prospects of the investee. Realized gains and losses are determined based on the specific identification method and are reported in other income (expense), net in the condensed consolidated statements of operations. If the Company determines that the decline in an investment’s fair value is other-than-temporary, the difference is recognized as an impairment loss in the condensed consolidated statements of operations.
Concentrations of credit risk	Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, accounts receivable, and short-term investments. The Company places its cash and cash equivalents and short-term investments with well-established financial institutions. Trade accounts receivables are typically unsecured and are derived from revenue earned from customers located around the world.
Non-trade receivables	The Company records non-trade receivables to reflect amounts due for activities outside of its subscription agreements, such as receivables resulting from tenant improvement allowances prior to the adoption of ASC 842.
Property and equipment, net	Equipment is stated at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful life of the related asset, which is generally three to seven years. Leasehold improvements are amortized on a straight-line basis over the shorter of their estimated useful lives or the term of the related lease. The following table presents the estimated useful lives of property and equipment: Property and equipment Useful life Buildings 20 to 30 years Datacenter and other computer equipment 3 to 5 years Office equipment and other 3 to 7 years Leasehold improvements Lesser of estimated useful life or remaining lease term
Lease obligations	The Company leases office space, datacenters, and equipment under non-cancelable finance and operating leases with various expiration dates through 2033. The Company determines if an arrangement contains a lease at inception. Operating lease right-of-use assets and lease liabilities are recognized at the present value of the future lease payments at commencement date. The interest rate implicit in the Company’s operating leases is not readily determinable, and therefore an incremental borrowing rate is estimated to determine the present value of future payments. The estimated incremental borrowing rate factors in a hypothetical interest rate on a collateralized basis with similar terms, payments, and economic environments. Operating lease right-of-use assets also include any prepaid lease payments and lease incentives. Certain of the operating lease agreements contain rent concession, rent escalation, and option to renew provisions. Rent concession and rent escalation provisions are considered in determining the straight-line single lease cost to be recorded over the lease term. Single lease cost is recognized on a straight-line basis over the lease term commencing on the date the Company has the right to use the leased property. The lease terms may include options to extend or terminate the lease. The Company generally uses the base, non-cancelable, lease term when recognizing the lease assets and liabilities, unless it is reasonably certain that the option will be exercised. In addition, certain of the Company’s operating lease agreements contain tenant improvement allowances from its landlords. These allowances are accounted for as lease incentives and decrease the Company's right-of-use asset and reduce single lease cost over the lease term. The Company leases certain equipment from various third parties, through equipment financing leases. These leases either include a bargain purchase option, a full transfer of ownership at the completion of the lease term, or the terms of the leases are at least 75 percent of the useful lives of the assets and are therefore classified as finance leases. These leases are capitalized in property and equipment and the related amortization of assets under finance leases is included in depreciation and amortization expense in the Company’s condensed consolidated statements of operations. Initial asset values and finance lease obligations are based on the present value of future minimum lease payments. The Company’s finance lease agreements may contain lease and non-lease components. The non-lease components include payments for support on infrastructure equipment obtained via finance leases, which when not significant in relation to the overall agreement, are combined with the lease components and accounted for together as a single lease component.
Business combinations	The Company uses best estimates and assumptions to assign a fair value to the tangible and intangible assets acquired and liabilities assumed in business combinations as of the acquisition date. These estimates are inherently uncertain and subject to refinement. During the measurement period, which may be up to one year from the acquisition date, adjustments to the fair value of these tangible and intangible assets acquired and liabilities assumed may be recorded, with the corresponding offset to goodwill. Upon the conclusion of the measurement period or final determination of the fair value of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to the Company’s consolidated statements of operations.
Long-lived assets, including goodwill and other acquired intangible assets, net	The Company evaluates the recoverability of its property and equipment and finite-lived intangible assets for possible impairment whenever events or circumstances indicate that the carrying amount of such assets may not be recoverable. The evaluation is performed at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities. Recoverability of these assets is measured by a comparison of the carrying amounts to the future undiscounted cash flows the assets are expected to generate. If such review determines that the carrying amount of specific property and equipment or intangible assets is not recoverable, the carrying amount of such assets is reduced to its fair value. The Company reviews goodwill for impairment at least annually in the fourth quarter, or more frequently if events or changes in circumstances would more likely than not reduce the fair value of its single reporting unit below its carrying value. The Company has not recorded impairment charges on property and equipment, goodwill, or intangible assets for the periods presented in these condensed consolidated financial statements. Acquired property and equipment and finite-lived intangible assets are amortized over their useful lives. The Company evaluates the estimated remaining useful life of these assets when events or changes in circumstances warrant a revision to the remaining period of amortization. If the Company revises the estimated useful life assumption for any asset, the remaining unamortized balance is amortized or depreciated over the revised estimated useful life on a prospective basis.
Income taxes	Deferred income tax balances reflect the effects of temporary differences between the financial reporting and tax bases of the Company’s assets and liabilities using enacted tax rates expected to apply when taxes are actually paid or recovered. In addition, deferred tax assets are recorded for net operating loss and credit carryforwards. A valuation allowance is provided against deferred tax assets unless it is more likely than not that they will be realized based on all available positive and negative evidence. Such evidence includes, but is not limited to, recent cumulative earnings or losses, expectations of future taxable income by taxing jurisdiction, and the carry-forward periods available for the utilization of deferred tax assets. The Company uses a two-step approach to recognizing and measuring uncertain income tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates it is more likely than not that the position will be sustained on audit. The second step is to measure the tax benefit as the largest amount which is more than 50% likely of being realized upon ultimate settlement. The Company recognizes interest and penalties related to unrecognized tax benefits as income tax expense. Although the Company believes that it has adequately reserved for its uncertain tax positions, it can provide no assurance that the final tax outcome of these matters will not be materially different. The Company evaluates its uncertain tax positions on a regular basis and evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, such as the 2017 Tax Cuts and Jobs Act ("2017 Tax Reform Act"), correspondence with tax authorities during the course of an audit, and effective settlement of audit issues. To the extent that the final tax outcome of these matters is different than the amounts recorded, such differences will affect the provision for income taxes in the period in which such determination is made and could have a material impact on the Company’s financial condition and results of operations.
Fair value measurement	The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. The Company defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value measurements for assets and liabilities, the Company considers the principal or most advantageous market in which it would transact and the market-based risk measurements or assumptions that market participants would use in pricing the asset or liability, such as risks inherent in valuation techniques, transfer restrictions, and credit risk. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1 —Quoted prices in active markets for identical assets or liabilities. Level 2 —Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 —Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability.
Recently issued accounting pronouncements not yet adopted and Recently adopted accounting pronouncements	In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) . Most prominent among the changes in the standard is the recognition of right-of-use assets (“ROU assets”) and lease liabilities by lessees for certain leases classified as operating leases under current GAAP. The Company has made the policy election to not recognize a lease liability or right-of-use asset for short-term operating leases. The Company adopted the standard as of January 1, 2019, using the modified retrospective approach and has elected to use the optional transition method which allows the Company to apply the guidance of ASC 840, including disclosure requirements, in the comparative periods presented. In addition, the Company elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allowed the Company to carry forward the historical lease classification related to agreements entered prior to adoption. The most significant impact was the recognition of ROU assets and lease liabilities for operating leases. The adoption of the new standard resulted in the recording of additional operating ROU assets and lease liabilities of approximately $431.7 million and $502.4 million , respectively, as of January 1, 2019. The accounting for finance leases remained unchanged, except for the accounting for certain non-lease components. Lease and non-lease components will be accounted for as a single lease component if the non-lease component is determined to be insignificant to the total agreement. The cumulative impact of transition to retained earnings, recorded as of the adoption date, was not material. The standard did not materially impact consolidated net earnings and had no impact on cash flows. In February 2018, the FASB issued ASU No. 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . Under existing U.S. GAAP, the effects of changes in tax rates and laws on deferred tax balances are recorded as a component of income tax expense in the period in which the law was enacted. When deferred tax balances related to items originally recorded in accumulated other comprehensive income are adjusted, certain tax effects become stranded in accumulated other comprehensive income. The amendments in ASU No. 2018-02 allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the 2017 Tax Reform Act. The amendments in ASU No. 2018-02 also require certain disclosures about stranded tax effects. The Company adopted ASU No. 2018-02 on January 1, 2019. The adoption of the standard did not have a material impact on the Company's condensed consolidated financial statements. In June 2018, the FASB issued ASU No. 2018-07, Improvements to Nonemployee Share-Based Payment Accounting. Under existing U.S. GAAP, the measurement date for equity awards granted to nonemployees is the earlier of the performance commitment date or the date the performance is complete. The amendments in ASU No. 2018-07 allow for measurement of these awards on the grant date, consistent with equity awards granted to employees. The Company adopted ASU No. 2018-07 on January 1, 2019. The adoption of the standard did not have a material impact on the Company's condensed consolidated financial statements. In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost. It also eliminates the concept of other-than-temporary impairment and requires credit losses related to available-for-sale debt securities to be recorded through an allowance for credit losses rather than as a reduction in the amortized cost basis of the securities. These changes will result in more timely recognition of credit losses. The guidance is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact of adopting ASU No. 2016-13. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820), which amends disclosure requirements for fair value measurements by requiring new disclosures, modifying existing requirements, and eliminating others. The amendments are the result of a broader disclosure project, which aims to improve the effectiveness of disclosures. ASU No. 2018-13 is effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years. Early adoption is permitted. The Company does not expect the adoption to have a significant impact on its disclosures and is currently evaluating the timing of adopting ASU No. 2018-13. In August 2018, the FASB issued ASU No. 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40), Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. Under existing U.S. GAAP, there is diversity in practice in accounting for the costs of implementing cloud computing arrangements that are service contracts. The amendments in ASU No. 2018-15 amend the definition of a hosting arrangement and requires a customer in a hosting arrangement that is a service contract to capitalize certain costs as if the arrangement were an internal-use software project. The guidance is effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact and timing of adopting ASU No. 2018-15.
Goodwill	Goodwill represents the excess of the purchase price in a business combination over the fair value of net tangible and intangible assets acquired. Goodwill amounts are not amortized, but tested for impairment on an annual basis.
Net loss per share	The Company computes net loss per share using the two-class method required for multiple classes of common stock and participating securities. The rights, including the liquidation and dividend rights, of the Class A common stock and Class B common stock are substantially identical, other than voting rights. Accordingly, the Class A common stock and Class B common stock share equally in the Company’s net losses. Before the IPO, the Company’s outstanding securities also included convertible preferred stock. The holders of convertible preferred stock did not have a contractual obligation to share in the Company’s losses, and as a result, net losses were not allocated to these securities.

Description of the Business a_3

Description of the Business and Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Estimated Useful Lives of Property and Equipment	The following table presents the estimated useful lives of property and equipment: Property and equipment Useful life Buildings 20 to 30 years Datacenter and other computer equipment 3 to 5 years Office equipment and other 3 to 7 years Leasehold improvements Lesser of estimated useful life or remaining lease term Property and equipment, net consisted of the following: As of March 31, 2019 December 31, 2018 Datacenter and other computer equipment $ 682.8 $ 667.4 Furniture and fixtures 24.8 23.8 Leasehold improvements 153.8 150.5 Construction in process 60.6 32.8 Total property and equipment 922.0 874.5 Accumulated depreciation and amortization (581.1 ) (563.9 ) Property and equipment, net $ 340.9 $ 310.6

Cash, Cash Equivalents and Sh_2

Cash, Cash Equivalents and Short-Term Investments (Tables)	3 Months Ended
	Mar. 31, 2019
Cash and Cash Equivalents [Abstract]
Schedule of Cash, Cash Equivalents and Short-Term Investments	The amortized cost, unrealized gains and losses and estimated fair value of the Company's cash, cash equivalents and short-term investments as of March 31, 2019 and December 31, 2018 consisted of the following: As of March 31, 2019 Amortized Cost Unrealized Gain Unrealized Loss Estimated Fair Value Cash $ 109.8 $ — $ — $ 109.8 Cash equivalents: Money market funds 226.9 — — 226.9 Commercial paper 19.5 — — 19.5 Corporate notes and obligations 3.0 — — 3.0 Total cash and cash equivalents $ 359.2 $ — $ — $ 359.2 Investments Corporate notes and obligations 244.7 0.6 — 245.3 U.S. Treasury securities 193.0 — (0.1 ) 192.9 Certificates of deposit 52.2 — — 52.2 U.S. agency obligations 38.5 — — 38.5 Commercial Paper 27.1 — — 27.1 Total short-term investments 555.5 0.6 (0.1 ) 556.0 Total $ 914.7 $ 0.6 $ (0.1 ) $ 915.2 As of December 31, 2018 Amortized cost Unrealized gain Unrealized loss Estimated fair value Cash $ 103.0 $ — $ — $ 103.0 Cash equivalents Money market funds 355.5 — — 355.5 U.S. Treasury securities 33.4 — — $ 33.4 Commercial paper 27.4 — — 27.4 Total cash and cash equivalents $ 519.3 $ — $ — $ 519.3 Short-term investments Corporate notes and obligations 269.6 0.1 (0.5 ) 269.2 U.S. Treasury securities 176.0 — (0.1 ) 175.9 Certificates of deposit 70.6 — — 70.6 U.S. agency obligations 37.1 — — 37.1 Commercial paper 17.2 — — 17.2 Total short-term investments 570.5 0.1 (0.6 ) 570.0 Total $ 1,089.8 $ 0.1 $ (0.6 ) $ 1,089.3
Contractual Maturities of Short Term Investments	The following table presents the contractual maturities of the Company’s short-term investments as of March 31, 2019 : As of March 31, 2019 Amortized cost Estimated fair value Due within one year $ 337.9 $ 338.1 Due between one to three years 217.6 217.9 Total $ 555.5 $ 556.0

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of Fair Value Assets Measured On Recurring Basis	The following table presents information about the Company’s financial instruments that are measured at fair value on a recurring basis using the input categories discussed in Note 1: As of March 31, 2019 Level 1 Level 2 Level 3 Total Cash equivalents Money market funds $ 226.9 $ — $ — $ 226.9 Commercial paper — 19.5 — 19.5 Corporate notes and obligations — 3.0 — 3.0 Total cash equivalents $ 226.9 $ 22.5 $ — $ 249.4 Short-term investments Corporate notes and obligations — 245.3 — 245.3 U.S. Treasury securities — 192.9 — 192.9 Certificates of deposit — 52.2 — 52.2 U.S. agency obligations — 38.5 — 38.5 Commercial paper — 27.1 — 27.1 Total short-term investments — 556.0 — 556.0 Total cash equivalents and short-term investments $ 226.9 $ 578.5 $ — $ 805.4 As of December 31, 2018 Level 1 Level 2 Level 3 Total Cash equivalents Money market funds $ 355.5 $ — $ — $ 355.5 U.S. Treasury securities — 33.4 — 33.4 Commercial paper — 27.4 — 27.4 Total cash equivalents $ 355.5 $ 60.8 $ — $ 416.3 Short-term investments Corporate notes and obligations — 269.2 — 269.2 U.S. treasury securities — 175.9 — 175.9 Certificates of deposit — 70.6 — 70.6 U.S agency obligations — 37.1 — 37.1 Commercial paper — 17.2 — 17.2 Total short-term investments — $ 570.0 — 570.0 Total cash equivalents and short-term investments $ 355.5 $ 630.8 $ — $ 986.3

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	The following table presents the estimated useful lives of property and equipment: Property and equipment Useful life Buildings 20 to 30 years Datacenter and other computer equipment 3 to 5 years Office equipment and other 3 to 7 years Leasehold improvements Lesser of estimated useful life or remaining lease term Property and equipment, net consisted of the following: As of March 31, 2019 December 31, 2018 Datacenter and other computer equipment $ 682.8 $ 667.4 Furniture and fixtures 24.8 23.8 Leasehold improvements 153.8 150.5 Construction in process 60.6 32.8 Total property and equipment 922.0 874.5 Accumulated depreciation and amortization (581.1 ) (563.9 ) Property and equipment, net $ 340.9 $ 310.6

Business Combinations (Tables)

Business Combinations (Tables)	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Schedule of Purchase Consideration Transferred	The purchase consideration transferred consisted of the following: Purchase consideration Cash paid to common and preferred stockholders and vested option holders $ 175.2 Transaction costs paid by Dropbox on behalf of HelloSign 2.4 Fair value of assumed HelloSign options attributable to pre-combination services (1) 0.8 Purchase price adjustments (0.8 ) Total purchase consideration $ 177.6 (1) The fair value of option assumed were based upon the Black-Scholes option-pricing model.
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	Assets acquired: Cash and cash equivalents $ 5.5 Short-term investments 7.8 Acquisition-related intangible assets 44.6 Accounts receivable, prepaid and other assets 5.0 Total assets acquired $ 62.9 Liabilities assumed: Accounts payable, accrued and other liabilities $ 6.3 Deferred revenue 4.8 Deferred tax liability 6.9 Total liabilities assumed 18.0 Net assets acquired, excluding goodwill 44.9 Total purchase consideration 177.6 Estimated goodwill (2) $ 132.7 (2) The goodwill recognized was primarily attributable to the opportunity to expand the user base of the Company's platform. The goodwill is not deductible for U.S. federal income tax purposes.
Schedule of Finite-Lived Intangible Assets Acquired and Estimated Useful Lives	The fair value of the separately identifiable finite-lived intangible assets acquired and estimated weighted average useful lives are as follows: Estimated fair values Estimated weighted average useful lives (In years) Customer relationships $ 20.5 4.9 Developed technology 19.6 5.0 Trade name 4.5 5.0 Total acquisition-related intangible assets $ 44.6

Intangible Assets (Tables)

Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	Intangible assets consisted of the following: As of March 31, As of December 31, Weighted- (In years) 2019 2018 Developed technology $ 25.0 $ 47.0 4.9 Customer relationships 20.5 — 4.8 Software 20.0 19.2 2.2 Patents 13.0 13.0 7.9 Assembled workforce in asset acquisitions 12.6 12.6 1.6 Licenses 4.6 4.6 2.2 Trademarks and trade names 5.2 0.7 4.9 Other 3.3 3.3 6.0 Total intangibles 104.2 100.4 Accumulated amortization (46.8 ) (85.7 ) Intangible assets, net $ 57.4 $ 14.7
Schedule of Future Amortization Expense	Expected future amortization expense for intangible assets as of March 31, 2019 , is as follows: Remaining nine months of Fiscal 2019 $ 10.8 2020 13.6 2021 11.3 2022 8.0 2023 7.7 Thereafter 6.0 Total $ 57.4

Goodwill (Tables)

Goodwill (Tables)	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The changes in the carrying amounts of goodwill were as follows: Balance at December 31, 2018 $ 96.5 HelloSign acquisition 132.7 Effect of foreign currency translation 1.2 Balance at March 31, 2019 $ 230.4

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Components of Lease Expense and Other Information	The components of single lease cost were as follows: Three months ended March 31, 2019 March 31, 2018 Operating lease cost (1) $ 22.1 $ 21.9 Finance lease cost: Amortization of assets under finance lease 21.7 21.7 Interest 2.2 1.9 Total finance lease cost $ 23.9 $ 23.6 (1) Is presented gross of sublease income and includes short-term leases, which are immaterial Other information related to leases was as follows: Three months ended March 31, 2019 Supplemental Cash Flow Information: Cash paid for amounts included in the measurement of lease liabilities: Payments for operating leases included in cash from operating activities $ 23.0 Payments for finance leases included in cash from operating activities $ 2.2 Payments for finance leases included in cash from financing activities $ 26.2 Assets obtained in exchange for lease obligations: Operating leases $ 14.5 Finance leases $ 39.9 Weighted Average Remaining Lease Term (in years) Operating leases 9.7 Finance leases 2.8 Weighted Average Discount Rate Operating leases 4.4 % Finance leases 5.1 %
Maturities of Operating Lease Liabilities	Future minimum lease payments under non-cancellable leases as of March 31, 2019 were as follows: Year ending December 31, Operating leases (1) Finance leases 2019 (excluding the three months ended March 31, 2019) $ 64.8 $ 64.2 2020 84.6 56.2 2021 77.6 41.1 2022 70.3 27.4 2023 53.4 2.2 Thereafter 357.0 — Total future minimum lease payments 707.7 191.1 Less imputed interest (163.6 ) (13.7 ) Less tenant improvement receivables (28.5 ) — Total liability $ 515.6 $ 177.4 (1) Consists of future non-cancelable minimum rental payments under operating leases for the Company’s corporate offices and datacenters where the Company has possession, excluding rent payments from the Company’s sub-tenants and variable operating expenses. As of March 31, 2019, the Company is entitled to non-cancelable rent payments from its sub-tenants of $40.6 million, which will be collected over the next 4 years .
Maturities of Finance Lease Liabilities	Future minimum lease payments under non-cancellable leases as of March 31, 2019 were as follows: Year ending December 31, Operating leases (1) Finance leases 2019 (excluding the three months ended March 31, 2019) $ 64.8 $ 64.2 2020 84.6 56.2 2021 77.6 41.1 2022 70.3 27.4 2023 53.4 2.2 Thereafter 357.0 — Total future minimum lease payments 707.7 191.1 Less imputed interest (163.6 ) (13.7 ) Less tenant improvement receivables (28.5 ) — Total liability $ 515.6 $ 177.4 (1) Consists of future non-cancelable minimum rental payments under operating leases for the Company’s corporate offices and datacenters where the Company has possession, excluding rent payments from the Company’s sub-tenants and variable operating expenses. As of March 31, 2019, the Company is entitled to non-cancelable rent payments from its sub-tenants of $40.6 million, which will be collected over the next 4 years .

Accrued and Other Current Lia_2

Accrued and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2019
Payables and Accruals [Abstract]
Schedule Of Accrued And Other Current Liabilities	Accrued and other current liabilities consisted of the following: As of March 31, 2019 December 31, 2018 Non-income taxes payable $ 83.9 $ 75.7 Accrued legal and other external fees 34.2 28.1 Deferred rent — 41.0 Income taxes payable (0.1 ) 0.3 Other accrued and current liabilities 30.8 19.4 Total accrued and other current liabilities $ 148.8 $ 164.5

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2019
Stockholders' Equity Note [Abstract]
Schedule of Stock Option and Restricted Stock Activity	Stock option and restricted stock activity for the Plans was as follows for the three months ended March 31, 2019 : Options outstanding Restricted stock outstanding Number of shares available for issuance under the Plans Number of shares outstanding under the Plans Weighted- average exercise price per share Weighted- average remaining contractual term (In years) Aggregate intrinsic value Number of shares outstanding under the Plans Weighted- average grant date fair value per share Balance at December 31, 2018 57.1 1.3 $ 14.68 5.0 $ 9.1 25.0 $ 18.68 Additional shares authorized 21.2 — — — — Stock options assumed 0.9 0.9 6.02 — — Options exercised and RSUs released — (0.2 ) 5.15 (2.6 ) 17.42 Options and RSUs canceled 1.5 — — (1.5 ) 17.19 Shares repurchased for tax withholdings on release of restricted stock 1.0 — — — 17.42 Restricted stock and options granted (2.5 ) 0.2 22.63 2.3 23.79 Balance at March 31, 2019 79.2 2.2 $ 12.45 5.1 $ 21.7 23.2 $ 19.44 Vested at March 31, 2019 1.1 $ 15.71 5.1 $ 7.7 — $ — Unvested at March 31, 2019 1.1 $ 9.22 $ 14.0 23.2 $ 19.44
Schedule of Pre-Tax Intrinsic Value	The following table summarizes information about the pre-tax intrinsic value of options exercised during the three months ended March 31, 2019 and 2018 : Three months ended March 31, 2019 2018 Intrinsic value of options exercised $ 3.1 $ 1.7
Fair Value of Stock Options Assumptions Used	The fair value of stock options assumed were estimated using the following assumptions: Expected volatility 51.6 % Expected term (in years) 3.4 - 7.0 Risk-free interest rate 2.42% - 2.51% Dividend yield — %

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the calculation of basic and diluted net loss per share attributable to common stockholders during the periods presented. The shares issued in the IPO and the shares of Class A and Class B common stock issued upon conversion of the outstanding shares of convertible preferred stock in the IPO are included in the table below weighted for the period outstanding in the three months ended March 31, 2018 . Additionally, the voluntary conversions of Class B common stock into Class A common stock are included in the table below weighted for the period outstanding in the three months ended March 31, 2019 : Three months ended March 31, 2019 2018 Class A Class B Class A Class B Numerator: Net loss attributable to common stockholders $ (4.0 ) $ (3.7 ) $ (30.8 ) $ (434.7 ) Denominator: Weighted-average number of common shares outstanding used in computing basic and diluted net loss per common share 215.1 195.4 14.5 204.3 Net loss per common share, basic and diluted $ (0.02 ) $ (0.02 ) $ (2.13 ) $ (2.13 )
Schedule of Potentially Dilutive Securities Excluded from Computation of Earnings Per Share	The weighted-average impact of potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive was as follows: Three months ended 2019 2018 Restricted stock units 24.6 56.3 Options to purchase shares of common stock 1.8 4.9 Co-Founder Grants 14.7 14.7 Total 41.1 75.9

Geographic Areas (Tables)

Geographic Areas (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Long-lived Assets by Geographic Areas	The following table sets forth long-lived assets by geographic area: As of March 31, 2019 December 31, 2018 United States $ 324.9 $ 293.6 International (1) 16.0 17.0 Total property and equipment, net $ 340.9 $ 310.6 (1) No single country other than the United States had a property and equipment balance greater than 10% of total property and equipment, net, as of March 31, 2019 and December 31, 2018 .
Revenue by Geographic Areas	The following table sets forth revenue by geographic area for the three months ended March 31, 2019 and 2018 . Three months ended March 31, 2019 2018 United States $ 197.1 $ 161.6 International (1) 188.5 154.7 Total revenue $ 385.6 $ 316.3 (1) No single country outside of the United States accounted for more than 10% of total revenue during the three months ended March 31, 2019 and 2018 , respectively.

Description of the Business a_4

Description of the Business and Summary of Significant Accounting Policies - Initial Public Offering and Private Placement and Stock Split (Details) $ / shares in Units, $ in Millions	Apr. 03, 2018USD ($)	Mar. 28, 2018USD ($)$ / sharesshares	Mar. 27, 2018USD ($)$ / sharesshares	Mar. 26, 2018shares	Mar. 22, 2018USD ($)	Mar. 07, 2018	Mar. 31, 2019USD ($)shares	Mar. 31, 2018USD ($)shares	Dec. 31, 2018USD ($)
Conversion of Stock [Line Items]
Stock issued in IPO (in shares)			26,822,409
Share price of stock issued in IPO (in dollars per share) | $ / shares			$ 21
Proceeds from initial public offering and private placement | $			$ 538.2				$ 0	$ 638.2	$ 746.6
Offering costs | $			$ 6.9				$ 0	$ 0.9
Reverse stock split ratio						0.6667
Class B common stock
Conversion of Stock [Line Items]
Shares converted in conversion (in shares)							11,800,000
Class A common stock
Conversion of Stock [Line Items]
Shares issued in conversion (in shares)							11,800,000
Conversion of Convertible Preferred Stock to Class B Common Stock | Convertible preferred stock
Conversion of Stock [Line Items]
Shares converted in conversion (in shares)				147,310,563
Conversion of Convertible Preferred Stock to Class B Common Stock | Class B common stock
Conversion of Stock [Line Items]
Shares issued in conversion (in shares)				147,310,563
Conversion of Convertible Preferred Stock to Class A Common Stock | Convertible preferred stock
Conversion of Stock [Line Items]
Shares converted in conversion (in shares)				258,620
Conversion of Convertible Preferred Stock to Class A Common Stock | Class A common stock
Conversion of Stock [Line Items]
Shares issued in conversion (in shares)				258,620
Conversion of Class B Common Stock to Class A Common Stock | Class B common stock
Conversion of Stock [Line Items]
Shares converted in conversion (in shares)				2,609,951
Conversion of Class B Common Stock to Class A Common Stock | Class A common stock
Conversion of Stock [Line Items]
Shares issued in conversion (in shares)				2,609,951
Private Placement
Conversion of Stock [Line Items]
Proceeds from initial public offering and private placement | $		$ 100
Private Placement | Class A common stock
Conversion of Stock [Line Items]
Sale of stock (in shares)		4,761,905
Share price of stock sold in shares (in dollars per share) | $ / shares		$ 21
Underwriters Over-allotment Option | Class A common stock
Conversion of Stock [Line Items]
Sale of stock (in shares)		5,400,000
Share price of stock sold in shares (in dollars per share) | $ / shares		$ 21
Proceeds received in sale of stock | $	$ 108.4
Two-Tier RSUs
Conversion of Stock [Line Items]
Recognized cumulative unrecognized stock-based compensation | $					$ 418.7
Shares released (in shares)								26,800,000
Employer related payroll expense | $								$ 13.9

Description of the Business a_5

Description of the Business and Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenue, performance obligation, description of timing	one year or longer
Revenue recognized	$ 222.6	$ 188.2
Remaining performance obligation	$ 549.8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation satisfaction period	12 months

Description of the Business a_6

Description of the Business and Summary of Significant Accounting Policies - Stock-based Compensation (Details) shares in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2017shares	Mar. 31, 2019awardshares	Dec. 31, 2018shares
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of award types | award		2
One-Tier RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 years
Two-Tier RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 years
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)		2.3
Tranche One | One-Tier RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		1 year
Tranche One | Two-Tier RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		1 year
Co-Founder Grants | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	14.7	14.7	14.7
Co-Founder Grants | Tranche One | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Chief Executive Officer | Co-Founder Grants | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	10.3
Director | Co-Founder Grants | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	4.4

Description of the Business a_7

Description of the Business and Summary of Significant Accounting Policies - Concentration of Credit Risk (Details) - Trade and Other Receivables - Customer Concentration Risk	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Customer A
Concentration Risk [Line Items]
Concentration risk, percentage	13.00%	14.00%
Customer B
Concentration Risk [Line Items]
Concentration risk, percentage	41.00%	23.00%

Description of the Business a_8

Description of the Business and Summary of Significant Accounting Policies - Non-trade Receivables (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Non-trade receivables	$ 10.3	$ 46.2

Description of the Business a_9

Description of the Business and Summary of Significant Accounting Policies - Deferred Commissions, Net (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Capitalized Contract Cost [Line Items]
Additional contract costs deferred	$ 7,300,000	$ 9,800,000
Deferred contract costs, amortization period	5 years
Amortization of deferred commissions	$ 3,900,000	$ 2,400,000
Impairment loss related to deferred costs	0
Deferred Commissions | Prepaid Expenses and Other Current Assets
Capitalized Contract Cost [Line Items]
Deferred contract costs	15,900,000		$ 14,500,000
Deferred Commissions | Other Assets
Capitalized Contract Cost [Line Items]
Deferred contract costs	$ 40,300,000		$ 38,300,000

Description of the Business _10

Description of the Business and Summary of Significant Accounting Policies - Property and Equipment, Net (Details)	3 Months Ended
	Mar. 31, 2019
Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Minimum | Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	20 years
Minimum | Datacenter and other computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Minimum | Office equipment and other
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	7 years
Maximum | Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	30 years
Maximum | Datacenter and other computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	5 years
Maximum | Office equipment and other
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	7 years

Description of the Business _11

Description of the Business and Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Details) - USD ($) $ in Millions	Mar. 31, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset	$ 430.4
Operating lease, liability	$ 515.6
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use asset		$ 431.7
Operating lease, liability		$ 502.4

Cash, Cash Equivalents and Sh_3

Cash, Cash Equivalents and Short-Term Investments - Schedule of Cash, Cash Equivalents and Short-Term Investments (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 359.2	$ 519.3
Total cash equivalents	359.2	519.3
Short-term investments, amortized cost	555.5	570.5
Short-term investments, unrealized gain	0.6	0.1
Short-term investments, unrealized loss	(0.1)	(0.6)
Short-term investments, estimated fair value	556	570
Total cash, cash equivalents, and short term investments, before unrealized gains (losses) on investments	914.7	1,089.8
Total cash, cash equivalents, and short term investments	915.2	1,089.3
Corporate notes and obligations
Cash and Cash Equivalents [Line Items]
Short-term investments, amortized cost	244.7	269.6
Short-term investments, unrealized gain	0.6	0.1
Short-term investments, unrealized loss	0	(0.5)
Short-term investments, estimated fair value	245.3	269.2
U.S. Treasury securities
Cash and Cash Equivalents [Line Items]
Short-term investments, amortized cost	193	176
Short-term investments, unrealized gain	0	0
Short-term investments, unrealized loss	(0.1)	(0.1)
Short-term investments, estimated fair value	192.9	175.9
Certificates of deposit
Cash and Cash Equivalents [Line Items]
Short-term investments, amortized cost	52.2	70.6
Short-term investments, unrealized gain	0	0
Short-term investments, unrealized loss	0	0
Short-term investments, estimated fair value	52.2	70.6
U.S. agency obligations
Cash and Cash Equivalents [Line Items]
Short-term investments, amortized cost	38.5	37.1
Short-term investments, unrealized gain	0	0
Short-term investments, unrealized loss	0	0
Short-term investments, estimated fair value	38.5	37.1
Commercial paper
Cash and Cash Equivalents [Line Items]
Short-term investments, amortized cost	27.1	17.2
Short-term investments, unrealized gain	0	0
Short-term investments, unrealized loss	0	0
Short-term investments, estimated fair value	27.1	17.2
Cash
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	109.8	103
Total cash equivalents	109.8	103
Money market funds
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	226.9	355.5
Total cash equivalents	226.9	355.5
U.S. Treasury securities
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents		33.4
Total cash equivalents		33.4
Commercial paper
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	19.5	27.4
Total cash equivalents	19.5	$ 27.4
Corporate notes and obligations
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	3
Total cash equivalents	$ 3

Cash, Cash Equivalents and Sh_4

Cash, Cash Equivalents and Short-Term Investments - Narrative (Details)	3 Months Ended
	Mar. 31, 2019USD ($)investment	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)
Cash and Cash Equivalents [Abstract]
Cash in transit for credit and debit card transactions	$ 15,800,000		$ 11,900,000
Number of investments in unrealized loss positions | investment	65
Other-than-temporary impairment loss	$ 0
Interest income	$ 6,200,000	$ 1,400,000

Cash, Cash Equivalents and Sh_5

Cash, Cash Equivalents and Short-Term Investments - Contractual Maturities of Short Term Investments (Details) $ in Millions	Mar. 31, 2019USD ($)
Amortized cost
Due within one year	$ 337.9
Due between one to three years	217.6
Total	555.5
Estimated fair value
Due within one year	338.1
Due between one to three years	217.9
Total	$ 556

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	$ 359.2	$ 519.3
Total short-term investments	556	570
Corporate notes and obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	245.3	269.2
U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	192.9	175.9
Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	52.2	70.6
U.S. agency obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	38.5	37.1
Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	27.1	17.2
Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	226.9	355.5
U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents		33.4
Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	19.5	27.4
Corporate notes and obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	3
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	556	570
Total cash equivalents and short-term investments	805.4	986.3
Fair Value, Measurements, Recurring | Corporate notes and obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	245.3	269.2
Fair Value, Measurements, Recurring | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	192.9	175.9
Fair Value, Measurements, Recurring | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	52.2	70.6
Fair Value, Measurements, Recurring | U.S. agency obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	38.5	37.1
Fair Value, Measurements, Recurring | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	27.1	17.2
Fair Value, Measurements, Recurring | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	226.9	355.5
Fair Value, Measurements, Recurring | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents		33.4
Fair Value, Measurements, Recurring | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	19.5	27.4
Fair Value, Measurements, Recurring | Corporate notes and obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	3
Fair Value, Measurements, Recurring | Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	249.4	416.3
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Total cash equivalents and short-term investments	226.9	355.5
Fair Value, Measurements, Recurring | Level 1 | Corporate notes and obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 1 | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 1 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 1 | U.S. agency obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 1 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 1 | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	226.9	355.5
Fair Value, Measurements, Recurring | Level 1 | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents		0
Fair Value, Measurements, Recurring | Level 1 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	0	0
Fair Value, Measurements, Recurring | Level 1 | Corporate notes and obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	0
Fair Value, Measurements, Recurring | Level 1 | Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	226.9	355.5
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	556	570
Total cash equivalents and short-term investments	578.5	630.8
Fair Value, Measurements, Recurring | Level 2 | Corporate notes and obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	245.3	269.2
Fair Value, Measurements, Recurring | Level 2 | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	192.9	175.9
Fair Value, Measurements, Recurring | Level 2 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	52.2	70.6
Fair Value, Measurements, Recurring | Level 2 | U.S. agency obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	38.5	37.1
Fair Value, Measurements, Recurring | Level 2 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	27.1	17.2
Fair Value, Measurements, Recurring | Level 2 | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	0	0
Fair Value, Measurements, Recurring | Level 2 | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents		33.4
Fair Value, Measurements, Recurring | Level 2 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	19.5	27.4
Fair Value, Measurements, Recurring | Level 2 | Corporate notes and obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	3
Fair Value, Measurements, Recurring | Level 2 | Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	22.5	60.8
Fair Value, Measurements, Recurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Total cash equivalents and short-term investments	0	0
Fair Value, Measurements, Recurring | Level 3 | Corporate notes and obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 3 | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 3 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 3 | U.S. agency obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 3 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	0	0
Fair Value, Measurements, Recurring | Level 3 | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	0	0
Fair Value, Measurements, Recurring | Level 3 | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents		0
Fair Value, Measurements, Recurring | Level 3 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	0	0
Fair Value, Measurements, Recurring | Level 3 | Corporate notes and obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	0
Fair Value, Measurements, Recurring | Level 3 | Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	$ 0	$ 0

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 922	$ 874.5
Accumulated depreciation and amortization	(581.1)	(563.9)
Property and equipment, net	340.9	310.6
Datacenter and other computer equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	682.8	667.4
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	24.8	23.8
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	153.8	150.5
Construction in process
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 60.6	$ 32.8

Property and Equipment, Net - N

Property and Equipment, Net - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 922		$ 874.5
Accumulated depreciation	581.1		563.9
Depreciation	43.1	$ 34.1
Infrastructure Assets Acquired Under Finance Lease Agreements
Property, Plant and Equipment [Line Items]
Property and equipment, gross			360.2
Accumulated depreciation	$ 196.2		211.7
Infrastructure Assets Held under Capital Leases
Property, Plant and Equipment [Line Items]
Property and equipment, gross			$ 362.8

Business Combinations - Schedul

Business Combinations - Schedule of Purchase Consideration (Details) - HelloSign Inc. $ in Millions	Feb. 08, 2019USD ($)
Business Acquisition [Line Items]
Fair value of assumed HelloSign options attributable to pre-combination services (1)	$ 0.8
Purchase price adjustments	(0.8)
Total purchase consideration	177.6
Preferred Stockholders and Vested Option Holders
Business Acquisition [Line Items]
Cash and transaction costs paid	175.2
HelloSign
Business Acquisition [Line Items]
Cash and transaction costs paid	$ 2.4

Business Combinations - Narrati

Business Combinations - Narrative (Details) - HelloSign Inc. - USD ($) $ in Millions	Feb. 08, 2019	Mar. 31, 2019
Business Acquisition [Line Items]
Purchase consideration, agreements with key personnel	$ 48.5
Acquired finite-lived intangible assets weighted average amortization period	4 years 10 months 24 days
Transaction costs		$ 1

Business Combinations - Assets

Business Combinations - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Mar. 31, 2019	Feb. 08, 2019	Dec. 31, 2018
Liabilities assumed:
Goodwill	$ 230.4		$ 96.5
HelloSign Inc.
Assets acquired:
Cash and cash equivalents		$ 5.5
Short-term investments		7.8
Acquisition-related intangible assets		44.6
Accounts receivable, prepaid and other assets		5
Total assets acquired		62.9
Liabilities assumed:
Accounts payable, accrued and other liabilities		6.3
Deferred revenue		4.8
Deferred tax liability		6.9
Total liabilities assumed		18
Net assets acquired, excluding goodwill		44.9
Total purchase consideration		177.6
Goodwill		$ 132.7

Business Combinations - Sched_2

Business Combinations - Schedule of Finite-Lived Intangible Assets Acquired and Weighted Average Useful Lives (Details) - HelloSign Inc. $ in Millions	Feb. 08, 2019USD ($)
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated fair values	$ 44.6
Estimated weighted average useful lives (In years)	4 years 10 months 24 days
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated fair values	$ 20.5
Estimated weighted average useful lives (In years)	4 years 10 months 24 days
Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated fair values	$ 19.6
Estimated weighted average useful lives (In years)	5 years
Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated fair values	$ 4.5
Estimated weighted average useful lives (In years)	5 years

Intangible Assets - Schedule of

Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 104.2	$ 100.4
Accumulated amortization	(46.8)	(85.7)
Intangible assets, net	57.4	14.7
Developed technology
Finite-Lived Intangible Assets [Line Items]
Total intangibles	25	47
Intangible assets, retired	$ 41.7
Developed technology | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	4 years 10 months 24 days
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 20.5	0
Customer relationships | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	4 years 9 months 18 days
Software
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 20	19.2
Software | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	2 years 2 months 12 days
Patents
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 13	13
Patents | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	7 years 10 months 24 days
Assembled workforce in asset acquisitions
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 12.6	12.6
Assembled workforce in asset acquisitions | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	1 year 7 months 6 days
Licenses
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 4.6	4.6
Licenses | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	2 years 2 months 12 days
Trademarks and trade names
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 5.2	0.7
Trademarks and trade names | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	4 years 10 months 24 days
Other
Finite-Lived Intangible Assets [Line Items]
Total intangibles	$ 3.3	$ 3.3
Other | Weighted Average
Finite-Lived Intangible Assets [Line Items]
Weighted- average remaining useful life (In years)	6 years

Intangible Assets - Schedule _2

Intangible Assets - Schedule of Future Amortization Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 2.8	$ 1.8
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2019	10.8
2020	13.6
2021	11.3
2022	8
2023	7.7
Thereafter	6
Total	$ 57.4

Goodwill (Details)

Goodwill (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Balance at December 31, 2018	$ 96,500,000
HelloSign acquisition	132,700,000
Effect of foreign currency translation	1,200,000
Balance at March 31, 2019	230,400,000	$ 96,500,000
Goodwill impairment	$ 0	$ 0

Revolving Credit Facility (Deta

Revolving Credit Facility (Details) - Credit And Guarantee Agreement - Line of Credit - USD ($)	Apr. 30, 2017	Mar. 31, 2019	Feb. 28, 2018
Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 600,000,000		$ 725,000,000
Debt issuance fees	$ 2,600,000		400,000
Debt instrument, term	5 years
Line of credit facility, accordion feature, increase limit			275,000,000
Unused capacity, commitment fee percentage	0.20%
Covenant terms, minimum liquidity balance	$ 100,000,000
Aggregate letters of credit outstanding amount		$ 68,900,000
Remaining borrowing capacity		$ 656,100,000
Revolving Credit Facility | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.50%
Revolving Credit Facility | Base Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.50%
Letter of Credit
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			$ 187,500,000
Commitment fee percentage	1.50%
Fronting fee	0.125%

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2017
Lessee, Lease, Description [Line Items]
Lease, renewal term	5 years
Sublease income	$ 1,900,000	$ 3,500,000
Lease incentive obligation	42,600,000
Minimum obligations			$ 843,100,000
Tenant improvements			75,000,000
Tenant improvement allowance reimbursement	(13,800,000)	$ 0
Operating leases, not yet commenced, value	$ 408,300,000
Minimum
Lessee, Lease, Description [Line Items]
Lease, remaining lease term	1 year
Operating sublease, term	3 years
Operating leases, not yet commenced, term of contract	4 years
Maximum
Lessee, Lease, Description [Line Items]
Lease, remaining lease term	15 years
Operating sublease, term	4 years
Operating leases, not yet commenced, term of contract	15 years
Line of Credit | Letter of Credit | Corporate Headquarters Lease
Lessee, Lease, Description [Line Items]
Letter of credit			$ 34,200,000

Leases - Components of Lease Ex

Leases - Components of Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Leases [Abstract]
Operating lease cost	$ 22.1	$ 21.9
Finance Lease, Cost [Abstract]
Amortization of assets under finance lease	21.7	21.7
Interest	2.2	1.9
Finance Lease, Cost	$ 23.9	$ 23.6

Leases - Other Lease Informatio

Leases - Other Lease Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Payments for operating leases included in cash from operating activities	$ 23
Payments for finance leases included in cash from operating activities	2.2
Payments for finance leases included in cash from financing activities	26.2
Assets obtained in exchange for lease obligations: operating leases	14.5
Assets obtained in exchange for lease obligations: finance leases	$ 39.9
Weighted average remaining lease term (in years) - operating leases	9 years 8 months 12 days
Weighted average remaining lease term (in years) - finance leases	2 years 9 months 18 days
Weighted average discount rate - operating leases	4.40%
Weighted average discount rate - finance leases	5.10%

Leases - Future Minimum Lease P

Leases - Future Minimum Lease Payments (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Operating leases
2019	$ 64.8
2020	84.6
2021	77.6
2022	70.3
2023	53.4
Thereafter	357
Total future minimum lease payments	707.7
Less imputed interest	(163.6)
Less tenant improvement receivables	(28.5)
Operating lease, liability	515.6
Finance Lease Liabilities, Payments, Due [Abstract]
2019	64.2
2020	56.2
2021	41.1
2022	27.4
2023	2.2
Thereafter	0
Total future minimum lease payments	191.1
Less imputed interest	(13.7)
Less tenant improvement receivables	0
Finance lease, liability	177.4
Rent payments from sub-tenants	$ 40.6
Rent payments from sub-tenants, term	4 years

Accrued and Other Current Lia_3

Accrued and Other Current Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Non-income taxes payable	$ 83.9	$ 75.7
Accrued legal and other external fees	34.2	28.1
Deferred rent	0	41
Income taxes payable	(0.1)	0.3
Other accrued and current liabilities	30.8	19.4
Total accrued and other current liabilities	$ 148.8	$ 164.5

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock, Convertible Preferred Stock, Preferred Stock (Details)	Mar. 26, 2018shares	Dec. 31, 2017shares	Mar. 31, 2019vote$ / sharesshares	Dec. 31, 2018shares
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)			240,000,000
Restricted Stock
Class of Stock [Line Items]
Shares granted (in shares)			2,300,000
Co-Founder Grants | Restricted Stock
Class of Stock [Line Items]
Shares granted (in shares)		14,700,000	14,700,000	14,700,000
Class A common stock
Class of Stock [Line Items]
Votes per share | vote			1
Common stock, shares authorized (in shares)			2,400,000,000
Common stock, par value (in dollars per share) | $ / shares			$ 0.00001
Common stock, shares issued (in shares)			224,100,000	211,000,000
Common stock, shares outstanding (in shares)			224,100,000	211,000,000
Shares issued in conversion (in shares)			11,800,000
Class A common stock | Conversion of Convertible Preferred Stock to Class A Common Stock
Class of Stock [Line Items]
Shares issued in conversion (in shares)	258,620
Class B common stock
Class of Stock [Line Items]
Votes per share | vote			10
Shares converted in conversion (in shares)			11,800,000
Common stock, shares authorized (in shares)			475,000,000
Common stock, par value (in dollars per share) | $ / shares			$ 0.00001
Common stock, shares issued (in shares)			187,300,000	198,600,000
Common stock, shares outstanding (in shares)			187,300,000	198,600,000
Class B common stock | Conversion of Convertible Preferred Stock to Class B Common Stock
Class of Stock [Line Items]
Shares issued in conversion (in shares)	147,310,563
Class C common stock
Class of Stock [Line Items]
Votes per share | vote			0
Common stock, shares authorized (in shares)			800,000,000
Common stock, par value (in dollars per share) | $ / shares			$ 0.00001
Common stock, shares issued (in shares)			0	0
Common stock, shares outstanding (in shares)			0	0
Convertible preferred stock | Conversion of Convertible Preferred Stock to Class B Common Stock
Class of Stock [Line Items]
Shares converted in conversion (in shares)	147,310,563
Convertible preferred stock | Conversion of Convertible Preferred Stock to Class A Common Stock
Class of Stock [Line Items]
Shares converted in conversion (in shares)	258,620

Stockholders' Equity - Equity I

Stockholders' Equity - Equity Incentive Plans (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)	0.2
Shares issued and outstanding (in shares)	2.2		1.3
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of equity instruments other than options	$ 67.9	$ 643.3
2018 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Remaining unamortized stock-based compensation	$ 447.8
Unamortized stock-based compensation, requisite service period	3 years
2018 Plan | Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Vesting period	4 years
2008 Equity Incentive Plan, 2017 Equity Incentive Plan, and 2018 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued and outstanding (in shares)	25.4
Shares available for grant (in shares)	79.2

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Stock Option and Restricted Stock Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2019	Dec. 31, 2018
Number of shares available for issuance under the Plans
Beginning balance (in shares)	57.1
Additional shares authorized (in shares)	21.2
Stock options assumed (in shares)	0.9
Options and RSUs canceled (in shares)	1.5
Shares repurchased for tax withholdings on release of restricted stock (unaudited) (in shares)	1
Restricted stock granted (in shares)	(2.5)
Ending balance (in shares)	79.2	57.1
Options Outstanding, Number of shares outstanding under the Plans
Beginning balance (in shares)	1.3
Stock options assumed (in shares)	0.9
Options exercised (in shares)	(0.2)
Options granted (in shares)	0.2
Ending balance (in shares)	2.2	1.3
Vested during period (in shares)	1.1
Unvested at end of period (in shares)			1.1
Options Outstanding, Weighted- average exercise price per share
Beginning balance (in dollars per share)	$ 14.68
Stock options assumed (in dollars per share)	6.02
Options exercised (in dollars per share)	5.15
Ending balance (in dollars per share)	12.45	$ 14.68
Vested during period (in dollars per share)	$ 15.71
Unvested at end of period (in dollars per shares)			$ 9.22
Options Outstanding, Weighted- average remaining contractual term (In years)
Weighted-average contractual term	5 years 1 month 6 days	5 years
Vested during period	5 years 1 month 6 days
Options outstanding, aggregate intrinsic value			$ 21.7	$ 9.1
Vested during period, aggregate intrinsic value			7.7
Unvested during period, aggregate intrinsic value			$ 14
Restricted Stock
Restricted Stock Outstanding, Number of Plan shares outstanding
Beginning balance (in shares)	25
RSUs released (in shares)	(2.6)
RSUs canceled (in shares)	(1.5)
Restricted stock granted (in shares)	2.3
Ending balance (in shares)	23.2	25
Vested during period (in shares)	0
Unvested at end of period (in shares)	25	25	23.2	25
Restricted Stock Outstanding, Weighted- average grant date fair value per share
Beginning balance (in dollars per share)	$ 18.68
RSUs released (in dollars per share)	17.42
RSUs canceled (in dollars per share)	17.19
Shares repurchased for tax withholdings on release of restricted stock (in dollars per share)	17.42
Restricted stock granted (in dollars per share)	23.79
Ending balance (in dollars per share)	19.44	$ 18.68
Vested during period (in dollars per share)	0
Unvested at end of period (in dollars per share)	$ 18.68	$ 18.68	$ 19.44	$ 18.68

Stockholders' Equity - Schedu_2

Stockholders' Equity - Schedule of Pre-Tax Intrinsic Value (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Intrinsic value of options exercised	$ 3.1	$ 1.7

Stockholders' Equity - Assumed

Stockholders' Equity - Assumed Stock Options (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Feb. 08, 2019	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options assumed (in shares)		0.9
Weighted average grant date fair value of stock options assumed (in dollars per share)		$ 21.60
Fair value of options assumed in business combination		$ 19.4
Post combination, stock-based compensation expense		$ 18.6
HelloSign Inc.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options assumed (in shares)	0.9

Stockholders' Equity - Fair Val

Stockholders' Equity - Fair Value of Stock Option Assumptions Used (Details)	3 Months Ended
	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	51.60%
Risk-free interest rate, minimum	2.42%
Risk-free interest rate, maximum	2.51%
Dividend yield	0.00%
Employee Stock Option | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	3 years 4 months 24 days
Employee Stock Option | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	7 years

Stockholders' Equity - Co-Found

Stockholders' Equity - Co-Founder Grants and Award Modifications (Details) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Dec. 31, 2017USD ($)tranche$ / sharesshares	Mar. 31, 2019USD ($)$ / sharesshares	Mar. 31, 2018USD ($)	Dec. 31, 2018shares	Dec. 31, 2017USD ($)tranche$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value (in dollars per share) | $ / shares		$ 9.22
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)		2.3
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incremental stock based compensation | $			$ 10
Co-Founder Grants | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	14.7	14.7		14.7
Expiration period	10 years
Number of tranches | tranche	9				9
Weighted average grant date fair value (in dollars per share) | $ / shares	$ 10.60				$ 10.60
Unamortized stock-based compensation, requisite service period					5 years 2 months 12 days
Remaining unamortized stock-based compensation | $	$ 156.2	$ 119.3			$ 156.2
Stock-based compensation related to the Co-Founder Grants | $		$ 8.6	$ 10.6
Co-Founder Grants | Restricted Stock | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unamortized stock-based compensation, requisite service period					2 years 10 months 25 days
Co-Founder Grants | Restricted Stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unamortized stock-based compensation, requisite service period					6 years 10 months 25 days
Co-Founder Grants | Restricted Stock | Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Co-Founder Grants | Restricted Stock | Tranche One | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage vested maximum	20.00%
Co-Founder Grants | Chief Executive Officer | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	10.3
Co-Founder Grants | Director | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	4.4

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Class of Stock [Line Items]
Net loss attributable to common stockholders	$ (7.7)	$ (465.5)
Weighted-average number of common shares outstanding used in computing basic and diluted net loss per common share (in shares)	410.5	218.8
Net loss per common share, basic and diluted (in dollars per share)	$ (0.02)	$ (2.13)
Class A
Class of Stock [Line Items]
Net loss attributable to common stockholders	$ (4)	$ (30.8)
Weighted-average number of common shares outstanding used in computing basic and diluted net loss per common share (in shares)	215.1	14.5
Net loss per common share, basic and diluted (in dollars per share)	$ (0.02)	$ (2.13)
Class B
Class of Stock [Line Items]
Net loss attributable to common stockholders	$ (3.7)	$ (434.7)
Weighted-average number of common shares outstanding used in computing basic and diluted net loss per common share (in shares)	195.4	204.3
Net loss per common share, basic and diluted (in dollars per share)	$ (0.02)	$ (2.13)

Net Loss Per Share - Schedule_2

Net Loss Per Share - Schedule of Potentially Dilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	41.1	75.9
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	24.6	56.3
Options to purchase shares of common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1.8	4.9
Co-Founder Grants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	14.7	14.7

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)	$ (5.7)	$ 1.8
Increase in unrecognized tax benefits	3.6
Unrecognized tax benefits that would impact effective tax rate	0.6
HelloSign Inc.
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)	(6.9)
Deferred tax liability	$ 6.9

Related Party Transactions (Det

Related Party Transactions (Details) - Controlling Shareholders - Dropbox Charitable Foundation	3 Months Ended	12 Months Ended
	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2016shareholder
Related Party Transaction [Line Items]
Number of controlling shareholders in related party transaction | shareholder			2
Payments to related party | $	$ 0	$ 0

Geographic Areas (Details)

Geographic Areas (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Property and equipment, net	$ 340.9		$ 310.6
Revenue	385.6	$ 316.3
United States
Segment Reporting Information [Line Items]
Property and equipment, net	324.9		293.6
Revenue	197.1	161.6
International
Segment Reporting Information [Line Items]
Property and equipment, net	16		$ 17
Revenue	$ 188.5	$ 154.7

Uncategorized Items - dbx-20190

Label	Element	Value
Accounting Standards Update 2016-02 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 1,000,000
Accounting Standards Update 2016-02 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 1,000,000